diff --git a/app/helpers/blob_helper.rb b/app/helpers/blob_helper.rb
index bca53dfb88a8353211b9bfbd2f4905f5bd866944..15ed241f7e46b4069d154a5a200d8eef0ce81032 100644
--- a/app/helpers/blob_helper.rb
+++ b/app/helpers/blob_helper.rb
@@ -64,7 +64,7 @@ def encode_ide_path(path)
   def edit_blob_button(project = @project, ref = @ref, path = @path, options = {})
     return unless blob = readable_blob(options, path, project, ref)
 
-    common_classes = "btn btn-primary js-edit-blob gl-mr-3 #{options[:extra_class]}"
+    common_classes = "btn gl-button btn-confirm js-edit-blob gl-mr-3 #{options[:extra_class]}"
     data = { track_event: 'click_edit', track_label: 'Edit' }
 
     if Feature.enabled?(:web_ide_primary_edit, project.group)
@@ -84,7 +84,7 @@ def edit_blob_button(project = @project, ref = @ref, path = @path, options = {})
   def ide_edit_button(project = @project, ref = @ref, path = @path, blob:)
     return unless blob
 
-    common_classes = 'btn btn-primary ide-edit-button gl-mr-3'
+    common_classes = 'btn gl-button btn-confirm ide-edit-button gl-mr-3'
     data = { track_event: 'click_edit_ide', track_label: 'Web IDE' }
 
     unless Feature.enabled?(:web_ide_primary_edit, project.group)
@@ -105,7 +105,7 @@ def modify_file_button(project = @project, ref = @ref, path = @path, blob:, labe
     return unless current_user
     return unless blob
 
-    common_classes = "btn btn-#{btn_class}"
+    common_classes = "btn gl-button btn-default btn-#{btn_class}"
     base_button = button_tag(label, class: "#{common_classes} disabled", disabled: true)
 
     if !on_top_of_branch?(project, ref)
@@ -247,7 +247,7 @@ def copy_file_path_button(file_path)
   def copy_blob_source_button(blob)
     return unless blob.rendered_as_text?(ignore_errors: false)
 
-    clipboard_button(target: ".blob-content[data-blob-id='#{blob.id}'] > pre", class: "btn btn-sm js-copy-blob-source-btn", title: _("Copy file contents"))
+    clipboard_button(target: ".blob-content[data-blob-id='#{blob.id}'] > pre", class: "btn gl-button btn-default btn-sm js-copy-blob-source-btn", title: _("Copy file contents"))
   end
 
   def open_raw_blob_button(blob)
@@ -257,7 +257,7 @@ def open_raw_blob_button(blob)
     title = _('Open raw')
     link_to sprite_icon('doc-code'),
       external_storage_url_or_path(blob_raw_path),
-      class: 'btn btn-sm has-tooltip',
+      class: 'btn gl-button btn-default btn-sm has-tooltip',
       target: '_blank',
       rel: 'noopener noreferrer',
       aria: { label: title },
@@ -272,7 +272,7 @@ def download_blob_button(blob)
     link_to sprite_icon('download'),
       external_storage_url_or_path(blob_raw_path(inline: false)),
       download: @path,
-      class: 'btn btn-sm has-tooltip',
+      class: 'btn gl-button btn-default btn-sm has-tooltip',
       target: '_blank',
       rel: 'noopener noreferrer',
       aria: { label: title },
diff --git a/app/helpers/commits_helper.rb b/app/helpers/commits_helper.rb
index 2eb959856a5e9a3f14c4caca8e56c5e7d8733bc2..74c01caab9cba362fe370b6d50c4807c39b1fbf9 100644
--- a/app/helpers/commits_helper.rb
+++ b/app/helpers/commits_helper.rb
@@ -177,7 +177,7 @@ def view_on_environment_button(commit_sha, diff_new_path, environment)
     external_url = environment.external_url_for(diff_new_path, commit_sha)
     return unless external_url
 
-    link_to(external_url, class: 'btn btn-file-option has-tooltip', target: '_blank', rel: 'noopener noreferrer', title: "View on #{environment.formatted_external_url}", data: { container: 'body' }) do
+    link_to(external_url, class: 'btn gl-button btn-default btn-file-option has-tooltip', target: '_blank', rel: 'noopener noreferrer', title: "View on #{environment.formatted_external_url}", data: { container: 'body' }) do
       sprite_icon('external-link')
     end
   end
diff --git a/changelogs/unreleased/gl-button-file.yml b/changelogs/unreleased/gl-button-file.yml
new file mode 100644
index 0000000000000000000000000000000000000000..c6f7613471eb96c68a4cbb1c4183c9f6074efe6d
--- /dev/null
+++ b/changelogs/unreleased/gl-button-file.yml
@@ -0,0 +1,5 @@
+---
+title: Apply new GitLab UI for buttons in blob header
+merge_request: 52429
+author: Yogi (@yo)
+type: other
diff --git a/ee/app/views/projects/blob/_header_file_locks_link.html.haml b/ee/app/views/projects/blob/_header_file_locks_link.html.haml
index 7c6bbc684deb276e5d42d2bea8f81cbbd1529e24..0e10a52efe4f5d179f88b1f25b34acff67daa05e 100644
--- a/ee/app/views/projects/blob/_header_file_locks_link.html.haml
+++ b/ee/app/views/projects/blob/_header_file_locks_link.html.haml
@@ -1 +1 @@
-= lock_file_link(html_options: { class: 'btn btn-sm path-lock' })
+= lock_file_link(html_options: { class: 'btn gl-button btn-default btn-sm path-lock' })