diff --git a/spec/lucky/action_spec.cr b/spec/lucky/action_spec.cr
index 0f309f998..efd642f57 100644
--- a/spec/lucky/action_spec.cr
+++ b/spec/lucky/action_spec.cr
@@ -129,6 +129,8 @@ class OptionalParams::Index < TestAction
   param bool_with_false_default : Bool? = false
   # This is to test that an explicit 'nil' can be assigned for nilable types
   param nilable_with_explicit_nil : Int32? = nil
+  param nilable_array_with_default : Array(String)? = [] of String
+  param with_array_default : Array(Int32) = [26, 37, 44]
 
   get "/optional_params" do
     plain_text "optional param: #{page} #{with_int_default} #{with_int_never_nil}"
@@ -276,7 +278,7 @@ describe Lucky::Action do
     end
 
     it "returns optional param declarations" do
-      OptionalParams::Index.query_param_declarations.size.should eq 6
+      OptionalParams::Index.query_param_declarations.size.should eq 8
       OptionalParams::Index.query_param_declarations.should contain "bool_with_false_default : Bool | ::Nil"
     end
   end
@@ -388,6 +390,21 @@ describe Lucky::Action do
         OptionalParams::Index.new(build_context(path: "/?with_int_never_nil=no_int"), params()).call
       end
     end
+
+    it "allows nilable arrays with defaults" do
+      action = OptionalParams::Index.new(build_context(path: "/?page=3"), params)
+      action.nilable_array_with_default.should eq([] of String)
+    end
+
+    it "sets a value to a nilable array" do
+      action = OptionalParams::Index.new(build_context(path: "/?nilable_array_with_default[]=1&nilable_array_with_default[]=2"), params)
+      action.nilable_array_with_default.should eq(["1", "2"])
+    end
+
+    it "allows required arrays with defaults" do
+      action = OptionalParams::Index.new(build_context(path: "/?with_array_default=2222222"), params)
+      action.with_array_default.should eq([26, 37, 44])
+    end
   end
 end
 
diff --git a/spec/lucky/params_spec.cr b/spec/lucky/params_spec.cr
index f19780f91..6dea330d2 100644
--- a/spec/lucky/params_spec.cr
+++ b/spec/lucky/params_spec.cr
@@ -82,11 +82,11 @@ describe Lucky::Params do
 
     params = Lucky::Params.new(request)
 
-    params.nested?(:user)
-    params.nested?(:user)
+    params.nested?(:user).should eq({"name" => "Paul", "age" => "28"})
+    params.nested?(:user).should eq({"name" => "Paul", "age" => "28"})
   end
 
-  it "works when parsing multipart params twice" do
+  it "works when parsing json params twice" do
     request = build_request body: {page: 1}.to_json,
       content_type: "application/json",
       fixed_length: true
@@ -443,6 +443,109 @@ describe Lucky::Params do
     end
   end
 
+  describe "nested_arrays" do
+    it "gets nested arrays from form encoded params" do
+      request = build_request body: "user:name=paul&user:langs[]=ruby&user:langs[]=elixir",
+        content_type: "application/x-www-form-urlencoded"
+
+      params = Lucky::Params.new(request)
+
+      params.nested_arrays?(:user).should eq({"langs" => ["ruby", "elixir"]})
+    end
+
+    it "gets nested arrays from JSON params" do
+      request = build_request body: {user: {name: "Paul", langs: ["ruby", "elixir"]}}.to_json,
+        content_type: "application/json"
+      request.query = "from=query"
+
+      params = Lucky::Params.new(request)
+
+      params.nested_arrays?(:user).should eq({"langs" => ["ruby", "elixir"]})
+    end
+
+    it "gets empty JSON params when nested key is missing" do
+      request = build_request body: "{}",
+        content_type: "application/json"
+      request.query = "from=query"
+
+      params = Lucky::Params.new(request)
+
+      params.nested_arrays?(:user).should eq({} of String => JSON::Any)
+    end
+
+    it "handles JSON with charset directive in Content-Type header" do
+      request = build_request body: {user: {name: "Paul", langs: ["ruby", "elixir"]}}.to_json,
+        content_type: "application/json; charset=UTF-8"
+
+      params = Lucky::Params.new(request)
+
+      params.nested_arrays?(:user).should eq({"langs" => ["ruby", "elixir"]})
+    end
+
+    it "gets nested array JSON params mixed with query params" do
+      request = build_request body: {user: {name: "Bunyan", tags: ["tall"]}}.to_json,
+        content_type: "application/json"
+      request.query = "user:tags[]=tale"
+
+      params = Lucky::Params.new(request)
+
+      params.nested_arrays?(:user).should eq({"tags" => ["tall", "tale"]})
+    end
+
+    it "gets nested arrays from multipart params" do
+      request = build_multipart_request form_parts: {
+        "user:name" => "Paul", "user:langs" => ["ruby", "elixir"],
+      }
+
+      params = Lucky::Params.new(request)
+
+      params.nested_arrays?(:user).should eq({"langs" => ["ruby", "elixir"]})
+    end
+
+    it "gets nested arrays from query params" do
+      request = build_request body: "filter:toppings[]=sausage", content_type: ""
+      request.query = "filter:toppings[]=black_olive"
+      params = Lucky::Params.new(request)
+      params.nested_arrays?("filter").should eq({"toppings" => ["sausage", "black_olive"]})
+    end
+
+    it "returns an empty hash when no nested array is found" do
+      request = build_request body: "", content_type: ""
+      request.query = "a[]=1"
+      params = Lucky::Params.new(request)
+      params.nested_arrays?("a").empty?.should eq true
+    end
+
+    it "gets nested array params after unescaping" do
+      request = build_request body: "post%3Atags[]=coding",
+        content_type: "application/x-www-form-urlencoded"
+
+      params = Lucky::Params.new(request)
+
+      params.nested_arrays?(:post).should eq({"tags" => ["coding"]})
+    end
+
+    it "raises if nested array params are missing" do
+      request = build_request body: "",
+        content_type: "application/x-www-form-urlencoded"
+
+      params = Lucky::Params.new(request)
+
+      expect_raises Lucky::MissingNestedParamError do
+        params.nested_arrays(:missing)
+      end
+    end
+
+    it "returns empty hash if nested array params are missing" do
+      request = build_request body: "",
+        content_type: "application/x-www-form-urlencoded"
+
+      params = Lucky::Params.new(request)
+
+      params.nested_arrays?(:missing).should eq({} of String => Array(String))
+    end
+  end
+
   describe "get_file" do
     it "gets files" do
       request = build_multipart_request file_parts: {
@@ -524,6 +627,39 @@ describe Lucky::Params do
     end
   end
 
+  describe "nested_array_files" do
+    it "gets multipart nested array params" do
+      request = build_multipart_request file_parts: {
+        "user:photos" => ["cat", "dog"],
+      }
+
+      params = Lucky::Params.new(request)
+
+      files = params.nested_array_files(:user)["photos"]
+      files.size.should eq(2)
+      File.read(files[0].path).should eq("cat")
+      File.read(files[1].path).should eq("dog")
+    end
+
+    it "raises if nested array files are missing" do
+      request = build_multipart_request form_parts: {"this" => "that"}
+
+      params = Lucky::Params.new(request)
+
+      expect_raises Lucky::MissingNestedParamError do
+        params.nested_array_files(:missing)
+      end
+    end
+
+    it "returns empty hash if nested array files are missing" do
+      request = build_multipart_request form_parts: {"this" => "that"}
+
+      params = Lucky::Params.new(request)
+
+      params.nested_array_files?(:missing).should eq({} of String => Array(Lucky::UploadedFile))
+    end
+  end
+
   describe "many_nested" do
     it "gets nested form encoded params" do
       request = build_request body: "users[0]:name=paul&users[1]:twitter_handle=@paulamason&users[0]:twitter_handle=@paulsmith&users[1]:name=paula&something:else=1",
diff --git a/spec/support/multipart_helper.cr b/spec/support/multipart_helper.cr
index a68f1e4df..bcb48ca70 100644
--- a/spec/support/multipart_helper.cr
+++ b/spec/support/multipart_helper.cr
@@ -57,4 +57,10 @@ module MultipartHelper
       multipart_file_part(formdata, nested_name, nested_value)
     end
   end
+
+  private def multipart_file_part(formdata : HTTP::FormData::Builder, name : String, value : Array(String))
+    value.each do |val|
+      multipart_file_part(formdata, name + "[]", val)
+    end
+  end
 end
diff --git a/src/lucky/params.cr b/src/lucky/params.cr
index 4ae4e9328..17fccd5a8 100644
--- a/src/lucky/params.cr
+++ b/src/lucky/params.cr
@@ -212,6 +212,14 @@ class Lucky::Params
     multipart_files[key.to_s]?
   end
 
+  def get_all_files(key : String | Symbol) : Array(Lucky::UploadedFile)
+    get_all_files?(key) || raise Lucky::MissingParamError.new(key.to_s)
+  end
+
+  def get_all_files?(key : String | Symbol) : Array(Lucky::UploadedFile)
+    multipart_files.fetch_all(key.to_s)
+  end
+
   # Retrieve a nested value from the params
   #
   # Nested params often appear in JSON requests or Form submissions. If no key
@@ -255,6 +263,36 @@ class Lucky::Params
     end
   end
 
+  # Retrieve a nested array from the params
+  #
+  # Nested params often appear in JSON requests or Form submissions. If no key
+  # is found a `Lucky::MissingParamError` will be raised:
+  #
+  # ```
+  # params.nested_array("tags")    # {"tags" => ["Lucky", "Crystal"]}
+  # params.nested_array("missing") # Missing parameter: missing
+  # ```
+  def nested_arrays(nested_key : String | Symbol) : Hash(String, Array(String))
+    nested_params = nested_arrays?(nested_key)
+    if nested_params.keys.empty?
+      raise Lucky::MissingNestedParamError.new nested_key
+    else
+      nested_params
+    end
+  end
+
+  def nested_arrays?(nested_key : String | Symbol) : Hash(String, Array(String))
+    if json?
+      nested_array_json_params(nested_key.to_s).merge(nested_array_query_params(nested_key.to_s)) do |_k, v1, v2|
+        v1 + v2
+      end
+    else
+      nested_array_form_params(nested_key.to_s).merge(nested_array_query_params(nested_key.to_s)) do |_k, v1, v2|
+        v1 + v2
+      end
+    end
+  end
+
   # Retrieve a nested file from the params
   #
   # Nested params often appear in JSON requests or Form submissions. If no key
@@ -286,6 +324,19 @@ class Lucky::Params
     nested_file_params(nested_key.to_s)
   end
 
+  def nested_array_files(nested_key : String | Symbol) : Hash(String, Array(Lucky::UploadedFile))
+    nested_file_params = nested_array_files?(nested_key)
+    if nested_file_params.keys.empty?
+      raise Lucky::MissingNestedParamError.new nested_key
+    else
+      nested_file_params
+    end
+  end
+
+  def nested_array_files?(nested_key : String | Symbol) : Hash(String, Array(Lucky::UploadedFile))?
+    nested_array_file_params(nested_key.to_s)
+  end
+
   # Retrieve nested values from the params
   #
   # Nested params often appear in JSON requests or Form submissions. If no key
@@ -357,7 +408,7 @@ class Lucky::Params
 
   private def nested_json_params(nested_key : String) : Hash(String, String)
     nested_params = {} of String => String
-    nested_key_json = parsed_json[nested_key]? || JSON.parse("{}")
+    nested_key_json = parsed_json[nested_key]? || JSON::Any.new({} of String => JSON::Any)
 
     nested_key_json.as_h.each do |key, value|
       nested_params[key.to_s] = value.to_s
@@ -366,6 +417,19 @@ class Lucky::Params
     nested_params
   end
 
+  private def nested_array_json_params(nested_key : String) : Hash(String, Array(String))
+    nested_params = {} of String => Array(String)
+    nested_key_json = parsed_json[nested_key]? || JSON::Any.new({} of String => JSON::Any)
+
+    nested_key_json.as_h.each do |key, value|
+      if array_value = value.as_a?
+        nested_params[key.to_s] = array_value.map(&.to_s)
+      end
+    end
+
+    nested_params
+  end
+
   private def nested_form_params(nested_key : String) : Hash(String, String)
     nested_key = "#{nested_key}:"
     source = multipart? ? multipart_params : form_params
@@ -378,6 +442,22 @@ class Lucky::Params
     end
   end
 
+  private def nested_array_form_params(nested_key : String) : Hash(String, Array(String))
+    nested_key = "#{nested_key}:"
+    nested_params = {} of String => Array(String)
+
+    source = multipart? ? multipart_params : form_params
+    source.each do |key, value|
+      if key.starts_with?(nested_key) && key.ends_with?("[]")
+        new_key = key.lchop(nested_key).rchop("[]")
+        nested_params[new_key.to_s] ||= [] of String
+        nested_params[new_key.to_s] << value
+      end
+    end
+
+    nested_params
+  end
+
   private def nested_query_params(nested_key : String) : Hash(String, String)
     nested_key = "#{nested_key}:"
     query_params.to_h.reduce(empty_params) do |nested_params, (key, value)|
@@ -389,6 +469,20 @@ class Lucky::Params
     end
   end
 
+  private def nested_array_query_params(nested_key : String) : Hash(String, Array(String))
+    nested_key = "#{nested_key}:"
+    nested_params = {} of String => Array(String)
+    query_params.each do |key, value|
+      if key.starts_with?(nested_key) && key.ends_with?("[]")
+        new_key = key.lchop(nested_key).rchop("[]")
+        nested_params[new_key.to_s] ||= [] of String
+        nested_params[new_key.to_s] << value
+      end
+    end
+
+    nested_params
+  end
+
   private def nested_file_params(nested_key : String) : Hash(String, Lucky::UploadedFile)
     nested_key = "#{nested_key}:"
     multipart_files.to_h.reduce(empty_file_params) do |nested_params, (key, value)|
@@ -400,6 +494,21 @@ class Lucky::Params
     end
   end
 
+  private def nested_array_file_params(nested_key : String) : Hash(String, Array(Lucky::UploadedFile))
+    nested_key = "#{nested_key}:"
+    nested_params = {} of String => Array(Lucky::UploadedFile)
+
+    multipart_files.each do |key, value|
+      if key.starts_with?(nested_key) && key.ends_with?("[]")
+        new_key = key.lchop(nested_key).rchop("[]")
+        nested_params[new_key.to_s] ||= [] of Lucky::UploadedFile
+        nested_params[new_key.to_s] << value
+      end
+    end
+
+    nested_params
+  end
+
   private def zipped_many_nested_params(nested_key : String)
     body_params = many_nested_body_params(nested_key)
     query_params = many_nested_query_params(nested_key)
diff --git a/src/lucky/routable.cr b/src/lucky/routable.cr
index 0befe6e00..c9bb74595 100644
--- a/src/lucky/routable.cr
+++ b/src/lucky/routable.cr
@@ -401,16 +401,26 @@ module Lucky::Routable
   # ```
   #
   # When visiting this page, the path _must_ contain the token parameter:
-  # `/user_confirmations?token=abc123`
+  # `/user_confirmations/new?token=abc123`
   macro param(type_declaration)
+    {% unless type_declaration.is_a?(TypeDeclaration) %}
+      {% raise "'param' expects a type declaration like 'name : String', instead got: '#{type_declaration}'" %}
+    {% end %}
+
     {% PARAM_DECLARATIONS << type_declaration %}
     @@query_param_declarations << "{{ type_declaration.var }} : {{ type_declaration.type }}"
 
-    def {{ type_declaration.var }} : {{ type_declaration.type }}
-      {% is_nilable_type = type_declaration.type.is_a?(Union) %}
-      {% type = is_nilable_type ? type_declaration.type.types.first : type_declaration.type %}
+    getter {{ type_declaration.var }} : {{ type_declaration.type }} do
+      {% is_nilable_type = type_declaration.type.resolve.nilable? %}
+      {% base_type = is_nilable_type ? type_declaration.type.types.first : type_declaration.type %}
+      {% is_array = base_type.is_a?(Generic) %}
+      {% type = is_array ? base_type.type_vars.first : base_type %}
 
+      {% if is_array %}
+      val = params.get_all?(:{{ type_declaration.var.id }})
+      {% else %}
       val = params.get?(:{{ type_declaration.var.id }})
+      {% end %}
 
       if val.nil?
         default_or_nil = {{ type_declaration.value.is_a?(Nop) ? nil : type_declaration.value }}
@@ -425,9 +435,9 @@ module Lucky::Routable
         {% end %}
       end
 
-      result = {{ type }}::Lucky.parse(val)
+      result = {{ base_type }}.adapter.parse(val)
 
-      if result.is_a? {{ type }}::Lucky::SuccessfulCast
+      if result.is_a? Avram::Type::SuccessfulCast
         result.value
       else
         raise Lucky::InvalidParamError.new(