The Bit O' Red have tied down the pair for another season at the club and McMillan says that he is happy with life in the north-west
The Bit O' Red have secured the services of the 27-year-old defender, as well as forward Aaron Greene for another season as manager Ian Baraclough continues preparations for the 2014 campaign.
And McMillan, who joined the club from Bohemians in 2013, revealed that he was "settled" in the west and aiming to build on his start to life at the Showgrounds.
"I've settled here and now I want the new season to be one of consistency and establishing myself in the team," he told the club's official website.
"I was disappointed with the injuries I picked up this year. It was tough because I felt I was in good form before they occurred and it was difficult coming back into the side immediately.
"I'm pleased to have my future in Sligo secured and Ian is putting together a good squad already."