The 34-year-old arrives at the Bet Butler Stadium from Partick Thistle on an initial loan period until the January transfer window.
The move comes just 24 hours after the Championship side signed the forward Colin Nish, who was released by Hartlepool United in May and who will also coach Dumbarton's Under-19 as part of his duties.
Murray is best known for his time as a St Mirren player - he made 462 appearances for the Paisley outfit - and he is an inductee in the club's hall of fame. He played 16 times during Thistle's first division title-winning campaign.
He will bolster Dumbarton's midfield options with the club having endured a slow start to the season with just one win, a draw and two heavy defeats.