diff --git a/Library/Homebrew/dev-cmd/audit.rb b/Library/Homebrew/dev-cmd/audit.rb
index 08cb33977a..87faf0b725 100644
--- a/Library/Homebrew/dev-cmd/audit.rb
+++ b/Library/Homebrew/dev-cmd/audit.rb
@@ -435,40 +435,6 @@ module Homebrew
       end
     end
 
-    def audit_keg_only
-      return unless formula.keg_only?
-
-      whitelist = %w[
-        Apple
-        macOS
-        OS
-        Homebrew
-        Xcode
-        GPG
-        GNOME
-        BSD
-        Firefox
-      ].freeze
-
-      reason = formula.keg_only_reason.to_s
-      # Formulae names can legitimately be uppercase/lowercase/both.
-      name = Regexp.new(formula.name, Regexp::IGNORECASE)
-      reason.sub!(name, "")
-      first_word = reason.split.first
-
-      if reason =~ /\A[A-Z]/ && !reason.start_with?(*whitelist)
-        # TODO: check could be in RuboCop
-        problem <<~EOS
-          '#{first_word}' from the keg_only reason should be '#{first_word.downcase}'.
-        EOS
-      end
-
-      return unless reason.end_with?(".")
-
-      # TODO: check could be in RuboCop
-      problem "keg_only reason should not end with a period."
-    end
-
     def audit_postgresql
       return unless formula.name == "postgresql"
       return unless @core_tap
diff --git a/Library/Homebrew/rubocops.rb b/Library/Homebrew/rubocops.rb
index 6252f64b58..6b43b6f937 100644
--- a/Library/Homebrew/rubocops.rb
+++ b/Library/Homebrew/rubocops.rb
@@ -20,5 +20,6 @@ require "rubocops/lines"
 require "rubocops/class"
 require "rubocops/uses_from_macos"
 require "rubocops/files"
+require "rubocops/keg_only"
 
 require "rubocops/rubocop-cask"
diff --git a/Library/Homebrew/rubocops/keg_only.rb b/Library/Homebrew/rubocops/keg_only.rb
new file mode 100644
index 0000000000..e2969f2df1
--- /dev/null
+++ b/Library/Homebrew/rubocops/keg_only.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require "rubocops/extend/formula"
+
+module RuboCop
+  module Cop
+    module FormulaAudit
+      class KegOnly < FormulaCop
+        def audit_formula(_node, _class_node, _parent_class_node, body_node)
+          keg_only_node = find_node_method_by_name(body_node, :keg_only)
+          return unless keg_only_node
+
+          whitelist = %w[
+            Apple
+            macOS
+            OS
+            Homebrew
+            Xcode
+            GPG
+            GNOME
+            BSD
+            Firefox
+          ].freeze
+
+          reason = string_content(parameters(keg_only_node).first)
+          name = Regexp.new(@formula_name, Regexp::IGNORECASE)
+          reason = reason.sub(name, "")
+          first_word = reason.split.first
+
+          if reason =~ /\A[A-Z]/ && !reason.start_with?(*whitelist)
+            problem "'#{first_word}' from the keg_only reason should be '#{first_word.downcase}'."
+          end
+
+          return unless reason.end_with?(".")
+
+          problem "keg_only reason should not end with a period."
+        end
+      end
+    end
+  end
+end
diff --git a/Library/Homebrew/test/.rubocop_todo.yml b/Library/Homebrew/test/.rubocop_todo.yml
index d3da7961bc..a5a6d80cc5 100644
--- a/Library/Homebrew/test/.rubocop_todo.yml
+++ b/Library/Homebrew/test/.rubocop_todo.yml
@@ -46,6 +46,7 @@ RSpec/FilePath:
     - 'rubocops/conflicts_spec.rb'
     - 'rubocops/dependency_order_spec.rb'
     - 'rubocops/files_spec.rb'
+    - 'rubocops/keg_only_spec.rb'
     - 'rubocops/homepage_spec.rb'
     - 'rubocops/options_spec.rb'
     - 'rubocops/patches_spec.rb'
diff --git a/Library/Homebrew/test/dev-cmd/audit_spec.rb b/Library/Homebrew/test/dev-cmd/audit_spec.rb
index 895d339aef..132d70bf40 100644
--- a/Library/Homebrew/test/dev-cmd/audit_spec.rb
+++ b/Library/Homebrew/test/dev-cmd/audit_spec.rb
@@ -300,69 +300,6 @@ module Homebrew
       end
     end
 
-    describe "#audit_keg_only" do
-      specify "keg_only_needs_downcasing" do
-        fa = formula_auditor "foo", <<~RUBY, strict: true
-          class Foo < Formula
-            url "https://brew.sh/foo-1.0.tgz"
-
-            keg_only "Because why not"
-          end
-        RUBY
-
-        fa.audit_keg_only
-        expect(fa.problems)
-          .to eq(["'Because' from the keg_only reason should be 'because'.\n"])
-      end
-
-      specify "keg_only_redundant_period" do
-        fa = formula_auditor "foo", <<~RUBY, strict: true
-          class Foo < Formula
-            url "https://brew.sh/foo-1.0.tgz"
-
-            keg_only "because this line ends in a period."
-          end
-        RUBY
-
-        fa.audit_keg_only
-        expect(fa.problems)
-          .to eq(["keg_only reason should not end with a period."])
-      end
-
-      specify "keg_only_handles_block_correctly" do
-        fa = formula_auditor "foo", <<~RUBY, strict: true
-          class Foo < Formula
-            url "https://brew.sh/foo-1.0.tgz"
-
-            keg_only <<~EOF
-              this line starts with a lowercase word.
-
-              This line does not but that shouldn't be a
-              problem
-            EOF
-          end
-        RUBY
-
-        fa.audit_keg_only
-        expect(fa.problems)
-          .to eq([])
-      end
-
-      specify "keg_only_handles_whitelist_correctly" do
-        fa = formula_auditor "foo", <<~RUBY, strict: true
-          class Foo < Formula
-            url "https://brew.sh/foo-1.0.tgz"
-
-            keg_only "Apple ships foo in the CLT package"
-          end
-        RUBY
-
-        fa.audit_keg_only
-        expect(fa.problems)
-          .to eq([])
-      end
-    end
-
     describe "#audit_revision_and_version_scheme" do
       subject {
         fa = described_class.new(Formulary.factory(formula_path))
diff --git a/Library/Homebrew/test/rubocops/keg_only_spec.rb b/Library/Homebrew/test/rubocops/keg_only_spec.rb
new file mode 100644
index 0000000000..81112da206
--- /dev/null
+++ b/Library/Homebrew/test/rubocops/keg_only_spec.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+require "rubocops/keg_only"
+
+describe RuboCop::Cop::FormulaAudit::KegOnly do
+  subject(:cop) { described_class.new }
+
+  specify "keg_only_needs_downcasing" do
+    expect_offense(<<~RUBY)
+      class Foo < Formula
+
+        url "https://brew.sh/foo-1.0.tgz"
+        homepage "https://brew.sh"
+
+        keg_only "Because why not"
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^ 'Because' from the keg_only reason should be 'because'.
+      end
+    RUBY
+  end
+
+  specify "keg_only_redundant_period" do
+    expect_offense(<<~RUBY)
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        homepage "https://brew.sh"
+
+        keg_only "ending with a period."
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ keg_only reason should not end with a period.
+      end
+    RUBY
+  end
+
+  specify "keg_only_handles_block_correctly" do
+    expect_no_offenses(<<~RUBY)
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        homepage "https://brew.sh"
+
+        keg_only <<~EOF
+          this line starts with a lowercase word.
+
+          This line does not but that shouldn't be a
+          problem
+        EOF
+      end
+    RUBY
+  end
+
+  specify "keg_only_handles_whitelist_correctly" do
+    expect_no_offenses(<<~RUBY)
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        homepage "https://brew.sh"
+
+        keg_only "Apple ships foo in the CLT package"
+      end
+    RUBY
+  end
+
+  specify "keg_only does not need downcasing of formula name in reason" do
+    filename = Formulary.core_path("foo")
+    File.open(filename, "w") do |file|
+      FileUtils.chmod "-rwx", filename
+
+      expect_no_offenses(<<~RUBY, file)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+
+          keg_only "Foo is the formula name hence downcasing is not required"
+        end
+      RUBY
+    end
+  end
+end