The central defender joins from Partick Thistle after making 17 appearances for the Jags in the Premiership last season.
Prior to his spell at Firhill, Mair made over 100 appearances for St Mirren, while he has also turned out for Dundee, Stockport County, Dundee United and Aberdeen as well as loan spells with East Fife and Falkirk.
Mair made his Sons debut on Saturday, playing 45 minutes and helping Sons keep a clean sheet against Edinburgh City.
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