diff --git a/spec/open_api_spec.cr b/spec/open_api_spec.cr
index c064f3d..5b6308c 100644
--- a/spec/open_api_spec.cr
+++ b/spec/open_api_spec.cr
@@ -9,7 +9,7 @@ describe ActionController::OpenAPI do
   it "generates openapi docs" do
     result = ActionController::OpenAPI.generate_open_api_docs("title", "version", description: "desc")
     result[:openapi].should eq "3.0.3"
-    result[:paths].size.should eq 23
+    result[:paths].size.should eq 25
     result[:info][:description].should eq "desc"
   end
 end
diff --git a/spec/route_builder_spec.cr b/spec/route_builder_spec.cr
index 2261add..46660c1 100644
--- a/spec/route_builder_spec.cr
+++ b/spec/route_builder_spec.cr
@@ -186,4 +186,33 @@ describe AC::Route::Builder do
     result = client.get("/skipping_annotation")
     result.status_code.should eq 200
   end
+
+  it "should parse headers as params" do
+    result = client.get("/filtering/testing/header/values?query_param=12", headers: HTTP::Headers{
+      "X-Count" => "123",
+    })
+    result.status_code.should eq 200
+    result.body.should eq "123--12"
+
+    result = client.get("/filtering/testing/header/values/default?query_param=13")
+    result.status_code.should eq 200
+    result.body.should eq "12--13"
+
+    # test error handling
+    expect_raises(ActionController::Route::Param::MissingError, "missing required header 'X-Count'") do
+      client.get("/filtering/testing/header/values?query_param=12")
+    end
+
+    expect_raises(ActionController::Route::Param::ValueError, "invalid header value for 'X-Count'") do
+      client.get("/filtering/testing/header/values?query_param=12", headers: HTTP::Headers{
+        "X-Count" => "abc",
+      })
+    end
+
+    expect_raises(ActionController::Route::Param::ValueError, "invalid header value for 'X-Count'") do
+      client.get("/filtering/testing/header/values/default?query_param=12", headers: HTTP::Headers{
+        "X-Count" => "abc",
+      })
+    end
+  end
 end
diff --git a/spec/spec_helper.cr b/spec/spec_helper.cr
index b7c10ca..41c1b51 100644
--- a/spec/spec_helper.cr
+++ b/spec/spec_helper.cr
@@ -106,6 +106,24 @@ class Filtering < FilterOrdering
     id
   end
 
+  @[AC::Route::GET("/testing/header/values", content_type: "text/plain")]
+  def testing_headers(
+    @[AC::Param::Info(header: "X-Count", description: "number of requests made", example: "34")]
+    value : Int32,
+    query_param : Int32
+  ) : String
+    "#{value}--#{query_param}"
+  end
+
+  @[AC::Route::GET("/testing/header/values/default", content_type: "text/plain")]
+  def testing_headers_default(
+    query_param : Int32,
+    @[AC::Param::Info(header: "X-Count", description: "number of requests made", example: "34")]
+    value : Int32 = 12,
+  ) : String
+    "#{value}--#{query_param}"
+  end
+
   # Test default arguments and multiple routes for a single method
   @[AC::Route::GET("/other_route/:id/test")]
   @[AC::Route::GET("/other_route/test")]
diff --git a/src/action-controller/open_api.cr b/src/action-controller/open_api.cr
index 6ac36ad..d6e80f8 100644
--- a/src/action-controller/open_api.cr
+++ b/src/action-controller/open_api.cr
@@ -348,7 +348,7 @@ module ActionController::OpenAPI
           params: [
             {% for param_name, param in params %}
               {
-                name: {{ param_name }},
+                name: {{ param[:header] || param_name }},
                 in: {{ param[:in] }},
                 required: {{ param[:required] }},
                 schema: ::JSON::Schema.introspect({{ param[:schema] }}, openapi: true).to_json,
diff --git a/src/action-controller/router/builder.cr b/src/action-controller/router/builder.cr
index 2bcc150..fe1489d 100644
--- a/src/action-controller/router/builder.cr
+++ b/src/action-controller/router/builder.cr
@@ -387,6 +387,15 @@ module ActionController::Route::Builder
                       {% open_api_param = {} of Nil => Nil %}
                     {% else %}
                       {% open_api_param = open_api_params[query_param_name] || {} of Nil => Nil %}
+
+                      # check for header params
+                      {% if (ann_converter && ann_converter[:header]) %}
+                        {% open_api_param[:in] = :header %}
+                        {% open_api_param[:header] = ann_converter[:header].id.stringify %}
+                      {% else %}
+                        {% open_api_param[:in] = open_api_param[:in] || :query %}
+                      {% end %}
+
                       {% open_api_param[:in] = open_api_param[:in] || :query %}
                       {% open_api_param[:docs] = (ann_converter && ann_converter[:description]) %}
                       {% open_api_param[:example] = (ann_converter && ann_converter[:example]) %}
@@ -463,16 +472,26 @@ module ActionController::Route::Builder
                         {% end %}
                         end
 
+                      # handle header params
+                      {% elsif open_api_param.has_key?(:header) %}
+                        if param_value = @__context__.request.headers.fetch({{open_api_param[:header]}}, nil)
+                          {{restrictions.join(" || ").id}}
+                        {% if arg.default_value.stringify != "" %}
+                        else
+                          {{arg.default_value}}
+                        {% end %}
+                        end
+
                       # Required route param, so we ensure it
                       {% elsif required_params.includes? string_name %}
                         if param_value = route_params[{{query_param_name}}]?
                           {{restrictions.join(" || ").id}}
                         else
-                          raise ::AC::Route::Param::MissingError.new("missing required parameter", {{query_param_name}}, {{arg.restriction.resolve.stringify}})
+                          raise ::AC::Route::Param::MissingError.new("missing required parameter '#{ {{query_param_name}} }'", {{query_param_name}}, {{arg.restriction.resolve.stringify}})
                         end
 
-                      # An optional route param, might be passed as an query param
-                      {% else %}
+                      # An optional route param, might be passed as an query param (not the case for headers)
+                      {% elsif !open_api_param.has_key?(:header) %}
                         if param_value = params[{{query_param_name}}]?
                           {{restrictions.join(" || ").id}}
                         {% if arg.default_value.stringify != "" %}
@@ -485,11 +504,19 @@ module ActionController::Route::Builder
                     # Use tap to ensure a good error message if the function param isn't nilable
                     ){% if !nilable %}.tap { |result|
                       if result.nil?
-                        if params.has_key?({{query_param_name}})
-                          raise ::AC::Route::Param::ValueError.new("invalid parameter value", {{query_param_name}}, {{arg.restriction.resolve.stringify}})
-                        else
-                          raise ::AC::Route::Param::MissingError.new("missing required parameter", {{query_param_name}}, {{arg.restriction.resolve.stringify}})
-                        end
+                        {% if open_api_param.has_key?(:header) %}
+                          if @__context__.request.headers.has_key?({{open_api_param[:header]}})
+                            raise ::AC::Route::Param::ValueError.new("invalid header value for '#{ {{open_api_param[:header]}} }'", {{open_api_param[:header]}}, {{arg.restriction.resolve.stringify}})
+                          else
+                            raise ::AC::Route::Param::MissingError.new("missing required header '#{ {{open_api_param[:header]}} }'", {{open_api_param[:header]}}, {{arg.restriction.resolve.stringify}})
+                          end
+                        {% else %}
+                          if params.has_key?({{query_param_name}})
+                            raise ::AC::Route::Param::ValueError.new("invalid parameter value for '#{ {{query_param_name}} }'", {{query_param_name}}, {{arg.restriction.resolve.stringify}})
+                          else
+                            raise ::AC::Route::Param::MissingError.new("missing required parameter '#{ {{query_param_name}} }'", {{query_param_name}}, {{arg.restriction.resolve.stringify}})
+                          end
+                        {% end %}
                       end
                     }.not_nil!{% end %},
                   {% end %}