The attacking midfielder was on loan at MK Dons in 2013
Harley, 33, moves to MK Dons from Exeter after an agreement between all relevant parties was amicably agreed. He becomes the Club’s sixth signing of the summer.
“I’m really pleased to be here,” Harley, who has over 50 career goals to his name, told iFollow MK Dons. “This is obviously a big football club and I’m really looking forward to getting started.
“I’ve known the management team for a long time. I’m looking forward to playing for them again and linking up with a few of my friends.
“Hopefully it’ll be a successful year. It’s a tough division, as I’ve experienced over the past few years, but hopefully it’s one we’ll get through.”
Harley began his career with Bristol City before moving to Exeter City in January 2008. He scored 28 goals in 122 appearances for the Grecians, helping them achieve promotion from the National League and Sky Bet League Two, before joining Swansea City.
The midfielder later moved to Brighton & Hove Albion during which time he enjoyed a loan spell with MK Dons, scoring in the memorable 4-2 FA Cup victory over Queens Park Rangers. He then signed for Swindon Town before re-joining Paul Tisdale at Exeter in January 2015.
Last season, Harley made 26 appearances for Paul Tisdale’s side en route to their Sky Bet League Two play-off finish.
Manager Paul Tisdale said: “This is a very good signing for the Club. Ryan is someone I know very well and he will certainly help me and the team through this rebuilding process with his experience and knowhow but also with his undoubted ability."