diff --git a/lib/mongo/collection.rb b/lib/mongo/collection.rb
index c65fcee..1a9c632 100644
--- a/lib/mongo/collection.rb
+++ b/lib/mongo/collection.rb
@@ -321,6 +321,10 @@ module Mongo
     #
     # @return [ObjectId, Array]
     #   The _id of the inserted document or a list of _ids of all inserted documents.
+    # @return [[ObjectId, Array], [Hash, Array]]
+    #   1st, the _id of the inserted document or a list of _ids of all inserted documents.
+    #   2nd, a list of invalid documents as a BSON.
+    #   Return this result format when :collect_on_error is true.
     #
     # @option opts [Boolean, Hash] :safe (+false+)
     #   run the operation in safe mode, which run a getlasterror command on the
@@ -338,6 +342,8 @@ module Mongo
     #   if some are rejected on error. When safe mode is
     #   enabled, any error will raise an OperationFailure exception.
     #   MongoDB v2.0+.
+    # @option opts [Boolean] :collect_on_error (+false+) if true, then
+    #   collects invalid documents as a BSON. This option changes result format.
     #
     # @core insert insert-instance_method
     def insert(doc_or_docs, opts={})
@@ -944,10 +950,28 @@ module Mongo
       else
         message = BSON::ByteBuffer.new("\0\0\0\0")
       end
+
+      collect_on_error = !!flags[:collect_on_error]
+      error_docs = [] if collect_on_error
+
       BSON::BSON_RUBY.serialize_cstr(message, "#{@db.name}.#{collection_name}")
-      documents.each do |doc|
-        message.put_binary(BSON::BSON_CODER.serialize(doc, check_keys, true, @connection.max_bson_size).to_s)
-      end
+      documents =
+        if collect_on_error
+          documents.select do |doc|
+            begin
+              message.put_binary(BSON::BSON_CODER.serialize(doc, check_keys, true, @connection.max_bson_size).to_s)
+              true
+            rescue StandardError => e  # StandardError will be replaced with BSONError
+              doc.delete(:_id)
+              error_docs << doc
+              false
+            end
+          end
+        else
+          documents.each do |doc|
+            message.put_binary(BSON::BSON_CODER.serialize(doc, check_keys, true, @connection.max_bson_size).to_s)
+          end
+        end
       raise InvalidOperation, "Exceded maximum insert size of 16,000,000 bytes" if message.size > 16_000_000
 
       instrument(:insert, :database => @db.name, :collection => collection_name, :documents => documents) do
@@ -957,7 +981,13 @@ module Mongo
           @connection.send_message(Mongo::Constants::OP_INSERT, message)
         end
       end
-      documents.collect { |o| o[:_id] || o['_id'] }
+
+      doc_ids = documents.collect { |o| o[:_id] || o['_id'] }
+      if collect_on_error
+        return doc_ids, error_docs
+      else
+        doc_ids
+      end
     end
 
     def generate_index_name(spec)
diff --git a/test/collection_test.rb b/test/collection_test.rb
index ed90ca7..948131d 100644
--- a/test/collection_test.rb
+++ b/test/collection_test.rb
@@ -193,6 +193,41 @@ class TestCollection < Test::Unit::TestCase
     end
   end
 
+  def test_bson_invalid_key_serialize_error_with_collect_on_error
+    docs = []
+    docs << {:foo => 1}
+    docs << {:bar => 1}
+    invalid_docs = []
+    invalid_docs << {'$invalid-key' => 1}
+    invalid_docs << {'invalid.key'  => 1}
+    docs += invalid_docs
+    assert_raise BSON::InvalidKeyName do
+      @@test.insert(docs, :collect_on_error => false)
+    end
+    assert_equal 0, @@test.count
+
+    doc_ids, error_docs = @@test.insert(docs, :collect_on_error => true)
+    assert_equal 2, @@test.count
+    assert_equal error_docs, invalid_docs
+  end
+
+  def test_bson_invalid_encoding_serialize_error_with_collect_on_error
+    docs = []
+    docs << {:foo => 1}
+    docs << {:bar => 1}
+    invalid_docs = []
+    invalid_docs << {"\223\372\226{" => 1} # non utf8 encoding
+    docs += invalid_docs
+    assert_raise BSON::InvalidStringEncoding do
+      @@test.insert(docs, :collect_on_error => false)
+    end
+    assert_equal 0, @@test.count
+
+    doc_ids, error_docs = @@test.insert(docs, :collect_on_error => true)
+    assert_equal 2, @@test.count
+    assert_equal error_docs, invalid_docs
+  end
+
   def test_maximum_insert_size
     docs = []
     16.times do