diff --git a/NEWS b/NEWS
index 17f03af6b0..02b12f3d82 100644
--- a/NEWS
+++ b/NEWS
@@ -239,6 +239,13 @@ sufficient information, see the ChangeLog file or Redmine
     * Numeric#step now returns an instance of Enumerator::ArithmeticSequence
       class rather than one of Enumerator class.
 
+[OpenStruct]
+
+  [Modified methods]
+
+    * OpenStruct#to_h now maps keys and values to new keys and values
+      by the block if given.  [Feature #15143]
+
 [Proc]
 
   [New methods]
diff --git a/lib/ostruct.rb b/lib/ostruct.rb
index 67ba043535..eda539b614 100644
--- a/lib/ostruct.rb
+++ b/lib/ostruct.rb
@@ -104,16 +104,29 @@ def initialize_copy(orig) # :nodoc:
     @table = @table.dup
   end
 
+  #
+  # call-seq:
+  #   ostruct.to_h                        -> hash
+  #   ostruct.to_h {|name, value| block } -> hash
   #
   # Converts the OpenStruct to a hash with keys representing
   # each attribute (as symbols) and their corresponding values.
   #
+  # If a block is given, the results of the block on each pair of
+  # the receiver will be used as pairs.
+  #
   #   require "ostruct"
   #   data = OpenStruct.new("country" => "Australia", :capital => "Canberra")
   #   data.to_h   # => {:country => "Australia", :capital => "Canberra" }
+  #   data.to_h {|name, value| [name.to_s, value.upcase] }
+  #               # => {"country" => "AUSTRALIA", "capital" => "CANBERRA" }
   #
   def to_h
-    @table.dup
+    if block_given?
+      @table.to_h{|key, value| yield key, value}
+    else
+      @table.dup
+    end
   end
 
   #
diff --git a/spec/ruby/library/openstruct/to_h_spec.rb b/spec/ruby/library/openstruct/to_h_spec.rb
index f3e157816b..1a8a87a94d 100644
--- a/spec/ruby/library/openstruct/to_h_spec.rb
+++ b/spec/ruby/library/openstruct/to_h_spec.rb
@@ -26,4 +26,11 @@
     @to_h[:age] = 71
     @os.age.should == 70
   end
+
+  ruby_version_is "2.6" do
+    it "converts [key, value] pairs returned by the block to a hash" do
+      h = @os.to_h {|key, value| [key.to_s, value * 2]}
+      h.should == {"name" => "John SmithJohn Smith", "age" => 140, "pension" => 600}
+    end
+  end
 end
diff --git a/test/ostruct/test_ostruct.rb b/test/ostruct/test_ostruct.rb
index d89bc94cc3..61a4822810 100644
--- a/test/ostruct/test_ostruct.rb
+++ b/test/ostruct/test_ostruct.rb
@@ -141,6 +141,13 @@ def test_to_h
     assert_equal(h, OpenStruct.new("name" => "John Smith", "age" => 70, pension: 300).to_h)
   end
 
+  def test_to_h_with_block
+    os = OpenStruct.new("country" => "Australia", :capital => "Canberra")
+    assert_equal({"country" => "AUSTRALIA", "capital" => "CANBERRA" },
+                 os.to_h {|name, value| [name.to_s, value.upcase]})
+    assert_equal("Australia", os.country)
+  end
+
   def test_each_pair
     h = {name: "John Smith", age: 70, pension: 300}
     os = OpenStruct.new(h)