The 29-year-old centre-half joins Rovers following his release by the Seasiders and comes with League One experience having played for Bradford on loan last season.
Rovers boss Paul Dickov told the club’s official website: “Gary is a great signing for us, he is a quality defender with a footballing brain.
“He is a ‘hard as nails’ centre-half who comes highly recommended and a man who will run through brick walls for me, his team-mates and for the fans.
“Gary is what fans will call a proper centre-back.
“He is a player that has excelled in this league before and has had experience of getting into a play-off position and staying there which will be invaluable for us.
“Gary is also one of those players that won’t be happy with just a play-off position, he always wants more.
“He is exactly what we need in this squad, his strength of character, his mentality and the fact he has captained sides before will be invaluable for us, the lads and fans will love him.
“We are working very hard to bring even more players to the club, we could have had 10 in by now but we want the right players and sometimes you need to be patient to get them, Gary certainly fits this criteria.”
MacKenzie is Doncaster’s third summer signing and joins up with his new team-mates when they begin pre-season training on Wednesday.