McConnell said Republicans must come together to stop Obamacare and the rest of President Obama's agenda, The Hill reported.
"I'm a little tired of the hand-wringing. Conservatives were never meant to be part of the crybaby caucus," he said. "I know folks have a lot of opinions about what happened in November, but seriously, how many conferences and lunch panels do we really need to have about it?"
The 40th annual conference, held this year in National Harbor, Md., outside Washington, is often a showcase for potential presidential candidates. But the attendees also gave a warm welcome Friday to former Massachusetts Gov. Mitt Romney, who lost the last election, The New York Times said.
"It is up to us to make sure that we learn from my mistakes, and from our mistakes, so that we can win the victories those people and this nation depend upon,'' Romney said.
Romney praised the achievements of Republican governors. He said the party needs to learn from governors in Democratic and swing states, including in his list Bob McDonnell of Virginia and Chris Christie of New Jersey, who were not invited to this year's conference because of breaks with conservative orthodoxy.
On Thursday, Sen. Rand Paul, R-Ky., and other speakers attacked Sen. John McCain, R-Ariz., the Republican standard bearer in 2008.
"The GOP of old has grown stale and moss-covered," Paul, R-Ky., told the conference. "I don't think we need to name any names here, do we?"
The Washington Post said the reference to McCain was clear to everyone in the room, a largely youthful audience, with dozens waving red "Stand With Rand" posters.
The theme of the conference, which runs through Saturday, is "America's Future: The Next Generation of Conservatives; New Challenges, Timeless Principles."
McCain, 76, labeled Paul, 50, and other members of a new generation of conservative Republicans -- including Sen. Ted Cruz of Texas, 42, and libertarian Rep. Justin Amash of Michigan, 32 -- "wacko birds on the right."
McCain's comment to The Huffington Post March 7 came a day after libertarian Paul, aided by Cruz, conducted a 13-hour filibuster over the Obama administration's drone policy.
Also at the conference, hosted by the American Conservative Union Foundation, was Texas Gov. Rick Perry, who assailed McCain and Romney, saying they were not true conservatives.
"The popular media narrative is that this country has shifted away from conservative ideals, as evidenced by the last two presidential elections. That's what they think. That's what they say," said Perry.
"That might be true if Republicans had actually nominated conservative candidates in 2008 and 2012," he said to cheers and applause.
Perry himself was a candidate for the 2012 GOP nomination, but his bid ended after a series of debate performances widely considered lackluster.