In June 2013, after turning 50, Montgomerie joined the Champions Tour, where he made his debut in the Constellation Senior Players Championship, one of the five senior major championships. On 25 May 2014, Montgomerie won his first senior major championship at the Senior PGA Championship. He followed this up on 13 July 2014, when he claimed his second senior major at the U.S. Senior Open. On 24 May 2015, Montgomerie defended his Senior PGA Championship title to win his third senior major. However, in 2016 he narrowly missed out on making it three Senior PGA Championships in a row – finishing second and three shots behind winner Rocco Mediate. He won twice on the senior circuit in 2017, winning the inaugural Japan Airlines Championship before claiming his sixth Champions Tour win at the SAS Championship.