diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 61280dd..6a26232 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,7 +2,6 @@ name: CI
 on: [pull_request]
 jobs:
   test-skip-install-and-use-bundler:
-    name: runner / rubocop
     runs-on: ubuntu-latest
     defaults:
       run:
@@ -22,3 +21,55 @@ jobs:
           skip_install: 'true'
           use_bundler: 'true'
       - run: test "$(bundle exec rubocop --version)" == "1.18.1"
+  test-only_changed:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        shell: bash
+    env:
+      INPUT_ONLY_CHANGED: 'true'
+    steps:
+      - uses: actions/checkout@v4
+      - name: setup
+        run: |
+          git config user.email "workflow@github.com"
+          git config user.name "I am an automated workflow"
+      - name: Check when there are relevant files
+        run: |
+          git checkout ${{ github.sha }}
+          rm -f test/only_changed/reviewdog-was-called
+
+          cp test/only_changed/few_relevant/files/* .
+          git add *
+          git commit -m auto
+
+          export PATH=test/only_changed/few_relevant/mock_bins:test/only_changed/shared_mock_bins:$PATH
+          BASE_REF=$(git rev-parse HEAD~) HEAD_REF=$(git rev-parse HEAD) ./script.sh
+
+          [ -f test/only_changed/reviewdog-was-called ]
+      - name: Check when there are no relevant files
+        run: |
+          git checkout ${{ github.sha }}
+          rm -f test/only_changed/reviewdog-was-called
+
+          cp test/only_changed/nothing_relevant/files/* .
+          git add *
+          git commit -m auto
+
+          export PATH=test/only_changed/nothing_relevant/mock_bins:test/only_changed/shared_mock_bins:$PATH
+          BASE_REF=$(git rev-parse HEAD~) HEAD_REF=$(git rev-parse HEAD) ./script.sh
+
+          [ ! -f test/only_changed/reviewdog-was-called ]
+      - name: Check when there are too many relevant files
+        run: |
+          git checkout ${{ github.sha }}
+          rm -f test/only_changed/reviewdog-was-called
+
+          touch a{00..100}.rb
+          git add *
+          git commit -m auto
+
+          export PATH=test/only_changed/too_many_relevant/mock_bins:test/only_changed/shared_mock_bins:$PATH
+          BASE_REF=$(git rev-parse HEAD~) HEAD_REF=$(git rev-parse HEAD) ./script.sh
+
+          [ -f test/only_changed/reviewdog-was-called ]
diff --git a/README.md b/README.md
index 551328c..7fc2719 100644
--- a/README.md
+++ b/README.md
@@ -47,6 +47,14 @@ Default is `added`.
 Optional. Report level for reviewdog [`info`, `warning`, `error`].
 It's same as `-level` flag of reviewdog.
 
+### `only_changed`
+
+Optional. Run Rubocop only on changed (and added) files, for speedup [`true`, `false`].
+Default: `false`.
+
+Will fetch the tip of the base branch with depth 1 from remote origin if it is not available.
+If you use different remote name or customize the checkout otherwise, make the tip of the base branch available before this action
+
 ### `reporter`
 
 Optional. Reporter of reviewdog command [`github-pr-check`, `github-check`, `github-pr-review`].
diff --git a/action.yml b/action.yml
index e552ebe..530a5c1 100644
--- a/action.yml
+++ b/action.yml
@@ -19,6 +19,12 @@ inputs:
   level:
     description: 'Report level for reviewdog [info,warning,error]'
     default: 'error'
+  only_changed:
+    description: |
+      Run Rubocop only on changed (and added) files, for speedup [`true`, `false`].
+      Will fetch the tip of the base branch with depth 1 from remote origin if it is not available.
+      If you use different remote name or customize the checkout otherwise, make the tip of the base branch available before this action.
+    default: 'false'
   reporter:
     description: |
       Reporter of reviewdog command [github-pr-check,github-check,github-pr-review].
@@ -61,6 +67,7 @@ runs:
         INPUT_FILTER_MODE: ${{ inputs.filter_mode }}
         INPUT_GITHUB_TOKEN: ${{ inputs.github_token }}
         INPUT_LEVEL: ${{ inputs.level }}
+        INPUT_ONLY_CHANGED: ${{ inputs.only_changed }}
         INPUT_REPORTER: ${{ inputs.reporter }}
         INPUT_REVIEWDOG_FLAGS: ${{ inputs.reviewdog_flags }}
         INPUT_RUBOCOP_EXTENSIONS: ${{ inputs.rubocop_extensions }}
@@ -70,6 +77,8 @@ runs:
         INPUT_TOOL_NAME: ${{ inputs.tool_name }}
         INPUT_USE_BUNDLER: ${{ inputs.use_bundler }}
         INPUT_WORKDIR: ${{ inputs.workdir }}
+        BASE_REF: ${{ github.event.pull_request.base.sha }}
+        HEAD_REF: ${{ github.sha }}
 branding:
   icon: 'check-circle'
   color: 'red'
diff --git a/script.sh b/script.sh
index 81a06bc..b34f6b6 100755
--- a/script.sh
+++ b/script.sh
@@ -1,4 +1,7 @@
-#!/bin/sh -e
+#!/usr/bin/env bash
+
+set -e
+set -o pipefail
 
 cd "${GITHUB_WORKSPACE}/${INPUT_WORKDIR}" || exit
 export REVIEWDOG_GITHUB_API_TOKEN="${INPUT_GITHUB_TOKEN}"
@@ -85,9 +88,46 @@ else
   BUNDLE_EXEC="bundle exec "
 fi
 
+if [ "${INPUT_ONLY_CHANGED}" = "true" ]; then
+  echo '::group:: Getting changed files list'
+
+  # check if commit is present in repository, otherwise fetch it
+  if ! git cat-file -e "${BASE_REF}"; then
+    git fetch --depth 1 origin "${BASE_REF}"
+  fi
+
+  # get intersection of changed files (excluding deleted) with target files for
+  # rubocop as an array
+  # shellcheck disable=SC2086
+  readarray -t CHANGED_FILES < <(
+    comm -12 \
+      <(git diff --diff-filter=d --name-only "${BASE_REF}..${HEAD_REF}" | sort || kill $$) \
+      <(${BUNDLE_EXEC}rubocop --list-target-files | sort || kill $$)
+  )
+
+  if (( ${#CHANGED_FILES[@]} == 0 )); then
+    echo "No relevant files for rubocop, skipping"
+    exit 0
+  fi
+
+  printf '%s\n' "${CHANGED_FILES[@]}"
+
+  if (( ${#CHANGED_FILES[@]} > 100 )); then
+    echo "More than 100 changed files (${#CHANGED_FILES[@]}), running rubocop on all files"
+    unset CHANGED_FILES
+  fi
+
+  echo '::endgroup::'
+fi
+
 echo '::group:: Running rubocop with reviewdog 🐶 ...'
 # shellcheck disable=SC2086
-${BUNDLE_EXEC}rubocop ${INPUT_RUBOCOP_FLAGS} --require ${GITHUB_ACTION_PATH}/rdjson_formatter/rdjson_formatter.rb --format RdjsonFormatter \
+${BUNDLE_EXEC}rubocop \
+  ${INPUT_RUBOCOP_FLAGS} \
+  --require ${GITHUB_ACTION_PATH}/rdjson_formatter/rdjson_formatter.rb \
+  --format RdjsonFormatter \
+  --fail-level error \
+  "${CHANGED_FILES[@]}" \
   | reviewdog -f=rdjson \
       -name="${INPUT_TOOL_NAME}" \
       -reporter="${INPUT_REPORTER}" \
diff --git a/test/only_changed/few_relevant/files/a.rb b/test/only_changed/few_relevant/files/a.rb
new file mode 100644
index 0000000..5460224
--- /dev/null
+++ b/test/only_changed/few_relevant/files/a.rb
@@ -0,0 +1 @@
+puts "Hello, " + "world!"
diff --git a/test/only_changed/few_relevant/files/a.txt b/test/only_changed/few_relevant/files/a.txt
new file mode 100644
index 0000000..5460224
--- /dev/null
+++ b/test/only_changed/few_relevant/files/a.txt
@@ -0,0 +1 @@
+puts "Hello, " + "world!"
diff --git a/test/only_changed/few_relevant/mock_bins/rubocop b/test/only_changed/few_relevant/mock_bins/rubocop
new file mode 100755
index 0000000..bcd0014
--- /dev/null
+++ b/test/only_changed/few_relevant/mock_bins/rubocop
@@ -0,0 +1,18 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+case ARGV
+when %w[
+  --list-target-files
+]
+  puts Dir['**/*.rb']
+when %W[
+  --require #{ENV['GITHUB_ACTION_PATH']}/rdjson_formatter/rdjson_formatter.rb
+  --format RdjsonFormatter
+  --fail-level error
+  a.rb
+]
+  puts 'Mock message for reviewdog'
+else
+  abort "rubocop mock called with unexpected arguments:\n#{ARGV.join("\n")}"
+end
diff --git a/test/only_changed/nothing_relevant/files/a.txt b/test/only_changed/nothing_relevant/files/a.txt
new file mode 100644
index 0000000..5460224
--- /dev/null
+++ b/test/only_changed/nothing_relevant/files/a.txt
@@ -0,0 +1 @@
+puts "Hello, " + "world!"
diff --git a/test/only_changed/nothing_relevant/mock_bins/rubocop b/test/only_changed/nothing_relevant/mock_bins/rubocop
new file mode 100755
index 0000000..8b60d86
--- /dev/null
+++ b/test/only_changed/nothing_relevant/mock_bins/rubocop
@@ -0,0 +1,11 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+case ARGV
+when %w[
+  --list-target-files
+]
+  puts Dir['**/*.rb']
+else
+  abort "rubocop mock called with unexpected arguments:\n#{ARGV.join("\n")}"
+end
diff --git a/test/only_changed/shared_mock_bins/bundle b/test/only_changed/shared_mock_bins/bundle
new file mode 100755
index 0000000..0a28632
--- /dev/null
+++ b/test/only_changed/shared_mock_bins/bundle
@@ -0,0 +1,9 @@
+#!/bin/bash
+
+if [ "$1" = "exec" ]; then
+  shift
+  eval "$@"
+else
+  echo "Only 'exec' command is supported"
+  exit 1
+fi
diff --git a/test/only_changed/shared_mock_bins/curl b/test/only_changed/shared_mock_bins/curl
new file mode 100755
index 0000000..3c5bc23
--- /dev/null
+++ b/test/only_changed/shared_mock_bins/curl
@@ -0,0 +1,8 @@
+#!/bin/bash
+
+arguments="$*"
+
+if [ "$arguments" != "-sfL https://raw.githubusercontent.com/reviewdog/reviewdog/master/install.sh" ]; then
+  echo "curl mock got unexpected arguments: $arguments"
+  exit 1
+fi
diff --git a/test/only_changed/shared_mock_bins/reviewdog b/test/only_changed/shared_mock_bins/reviewdog
new file mode 100755
index 0000000..5334ef7
--- /dev/null
+++ b/test/only_changed/shared_mock_bins/reviewdog
@@ -0,0 +1,10 @@
+#!/bin/bash
+
+touch test/only_changed/reviewdog-was-called
+
+read -r input
+
+if [ "$input" != "Mock message for reviewdog" ]; then
+  echo "reviewdog mock got unexpected input: $input"
+  exit 1
+fi
diff --git a/test/only_changed/too_many_relevant/mock_bins/rubocop b/test/only_changed/too_many_relevant/mock_bins/rubocop
new file mode 100755
index 0000000..1a2a540
--- /dev/null
+++ b/test/only_changed/too_many_relevant/mock_bins/rubocop
@@ -0,0 +1,17 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+case ARGV
+when %w[
+  --list-target-files
+]
+  puts Dir['**/*.rb']
+when %W[
+  --require #{ENV['GITHUB_ACTION_PATH']}/rdjson_formatter/rdjson_formatter.rb
+  --format RdjsonFormatter
+  --fail-level error
+]
+  puts 'Mock message for reviewdog'
+else
+  abort "rubocop mock called with unexpected arguments:\n#{ARGV.join("\n")}"
+end