diff --git a/changelog/fix_an_error_when_inspecting_blank_heredoc_delimiter.md b/changelog/fix_an_error_when_inspecting_blank_heredoc_delimiter.md
new file mode 100644
index 000000000000..e0563dae4d40
--- /dev/null
+++ b/changelog/fix_an_error_when_inspecting_blank_heredoc_delimiter.md
@@ -0,0 +1 @@
+* [#11998](https://github.com/rubocop/rubocop/issues/11998): Fix an error when inspecting blank heredoc delimiter. ([@koic][])
diff --git a/lib/rubocop/cop/mixin/heredoc.rb b/lib/rubocop/cop/mixin/heredoc.rb
index 2ed16bb661bb..52f64f5cd7db 100644
--- a/lib/rubocop/cop/mixin/heredoc.rb
+++ b/lib/rubocop/cop/mixin/heredoc.rb
@@ -26,11 +26,15 @@ def indent_level(str)
       end
 
       def delimiter_string(node)
-        node.source.match(OPENING_DELIMITER).captures[1]
+        return '' unless (match = node.source.match(OPENING_DELIMITER))
+
+        match.captures[1]
       end
 
       def heredoc_type(node)
-        node.source.match(OPENING_DELIMITER).captures[0]
+        return '' unless (match = node.source.match(OPENING_DELIMITER))
+
+        match.captures[0]
       end
     end
   end
diff --git a/spec/rubocop/cop/naming/heredoc_delimiter_case_spec.rb b/spec/rubocop/cop/naming/heredoc_delimiter_case_spec.rb
index df309ed6451a..bb50c2267c8d 100644
--- a/spec/rubocop/cop/naming/heredoc_delimiter_case_spec.rb
+++ b/spec/rubocop/cop/naming/heredoc_delimiter_case_spec.rb
@@ -173,6 +173,14 @@
           RUBY
         end
       end
+
+      context 'when using blank heredoc delimiters' do
+        it 'does not register an offense' do
+          expect_no_offenses(<<~RUBY)
+            <<''
+          RUBY
+        end
+      end
     end
 
     context 'with a squiggly heredoc' do
diff --git a/spec/rubocop/cop/style/redundant_heredoc_delimiter_quotes_spec.rb b/spec/rubocop/cop/style/redundant_heredoc_delimiter_quotes_spec.rb
index 95b19111c2e3..842f69bf198f 100644
--- a/spec/rubocop/cop/style/redundant_heredoc_delimiter_quotes_spec.rb
+++ b/spec/rubocop/cop/style/redundant_heredoc_delimiter_quotes_spec.rb
@@ -161,4 +161,10 @@
       EOS
     RUBY
   end
+
+  it 'does not register an offense when using the blank heredoc delimiter' do
+    expect_no_offenses(<<~RUBY)
+      <<''
+    RUBY
+  end
 end