diff --git a/spec/ameba/formatter/github_actions_formatter_spec.cr b/spec/ameba/formatter/github_actions_formatter_spec.cr
new file mode 100644
index 000000000..12988d606
--- /dev/null
+++ b/spec/ameba/formatter/github_actions_formatter_spec.cr
@@ -0,0 +1,30 @@
+require "../../spec_helper"
+
+module Ameba::Formatter
+  describe GitHubActionsFormatter do
+    describe "#source_finished" do
+      it "writes valid source" do
+        output = IO::Memory.new
+        subject = GitHubActionsFormatter.new(output)
+
+        source = Source.new "", "/path/to/file.cr"
+
+        subject.source_finished(source)
+        output.to_s.should be_empty
+      end
+
+      it "writes invalid source" do
+        output = IO::Memory.new
+        subject = GitHubActionsFormatter.new(output)
+
+        source = Source.new "", "/path/to/file.cr"
+        location = Crystal::Location.new("/path/to/file.cr", 1, 2)
+
+        source.add_issue DummyRule.new, location, location, "message\n2nd line"
+
+        subject.source_finished(source)
+        output.to_s.should eq("::notice file=/path/to/file.cr,line=1,col=2,endLine=1,endColumn=2,title=Ameba/DummyRule::message%0A2nd line\n")
+      end
+    end
+  end
+end
diff --git a/src/ameba/config.cr b/src/ameba/config.cr
index 2c0b84f8e..89a710e53 100644
--- a/src/ameba/config.cr
+++ b/src/ameba/config.cr
@@ -39,12 +39,13 @@ class Ameba::Config
   include GlobUtils
 
   AVAILABLE_FORMATTERS = {
-    progress: Formatter::DotFormatter,
-    todo:     Formatter::TODOFormatter,
-    flycheck: Formatter::FlycheckFormatter,
-    silent:   Formatter::BaseFormatter,
-    disabled: Formatter::DisabledFormatter,
-    json:     Formatter::JSONFormatter,
+    progress:         Formatter::DotFormatter,
+    todo:             Formatter::TODOFormatter,
+    flycheck:         Formatter::FlycheckFormatter,
+    silent:           Formatter::BaseFormatter,
+    disabled:         Formatter::DisabledFormatter,
+    json:             Formatter::JSONFormatter,
+    "github-actions": Formatter::GitHubActionsFormatter,
   }
 
   XDG_CONFIG_HOME = ENV.fetch("XDG_CONFIG_HOME", "~/.config")
diff --git a/src/ameba/formatter/github_actions_formatter.cr b/src/ameba/formatter/github_actions_formatter.cr
new file mode 100644
index 000000000..dac1a9df4
--- /dev/null
+++ b/src/ameba/formatter/github_actions_formatter.cr
@@ -0,0 +1,69 @@
+module Ameba::Formatter
+  # A formatter that outputs issues in a GitHub Actions compatible format.
+  #
+  # See [GitHub Actions documentation](https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/workflow-commands-for-github-actions) for details.
+  class GitHubActionsFormatter < BaseFormatter
+    @mutex = Mutex.new
+
+    # Reports a result of the inspection of a corresponding source.
+    def source_finished(source : Source) : Nil
+      source.issues.each do |issue|
+        next if issue.disabled?
+
+        @mutex.synchronize do
+          output << "::"
+          output << command_name(issue.rule.severity)
+          output << " "
+          output << "file="
+          output << escape_property(source.path)
+          if location = issue.location
+            output << ",line="
+            output << location.line_number
+            output << ",col="
+            output << location.column_number
+          end
+          if end_location = issue.end_location
+            output << ",endLine="
+            output << end_location.line_number
+            output << ",endColumn="
+            output << end_location.column_number
+          end
+          output << ",title="
+          output << escape_property(issue.rule.name)
+          output << "::"
+          output << escape_data(issue.message)
+          output << "\n"
+        end
+      end
+    end
+
+    private def command_name(severity : Severity) : String
+      case severity
+      in .error?      then "error"
+      in .warning?    then "warning"
+      in .convention? then "notice"
+      end
+    end
+
+    # See for details:
+    # - https://github.com/actions/toolkit/blob/74906bea83a0dbf6aaba2d00b732deb0c3aefd2d/packages/core/src/command.ts#L92-L97
+    # - https://github.com/actions/toolkit/issues/193
+    private def escape_data(string : String) : String
+      string
+        .gsub('%', "%25")
+        .gsub('\r', "%0D")
+        .gsub('\n', "%0A")
+    end
+
+    # See for details:
+    # - https://github.com/actions/toolkit/blob/74906bea83a0dbf6aaba2d00b732deb0c3aefd2d/packages/core/src/command.ts#L99-L106
+    private def escape_property(string : String) : String
+      string
+        .gsub('%', "%25")
+        .gsub('\r', "%0D")
+        .gsub('\n', "%0A")
+        .gsub(':', "%3A")
+        .gsub(',', "%2C")
+    end
+  end
+end