An apparent electrical fire forced the detour on the flight from Omaha, Neb., to Los Angeles, campaign spokeswoman Andrea Saul said
The FAA says the chartered plane Mrs. Romney was on is a Canadair Regional Jet.
The plane landed on runway 35L and was greeted by Denver fire and police officials. Flight Support provided a shuttle for the passengers and the aircraft was towed off the runway.
DIA reports all operations are normal.
A photo tweeted by campaign officials shows fire crews entering the plane as it sits on the tarmac.
A spokesman traveling with Mitt Romney says Mrs. Romney told her husband everything was fine.
Romney was in Nevada, appearing at a fundraiser and rally on Friday. He did not mention the incident during a rally, but aides said he spoke to his wife from a car on the way to the event.
Mitt Romney later was heading to California for a weekend of fundraisers.
(KUSA-TV © 2012 Multimedia Holdings Corporation with The Associated Press)