The 26-year-old Hutton had been with the Sons' Championship rivals for a season but ended the campaign on loan to Airdrieonians in League One.
Hutton made 17 appearances for the Buddies but fell out of favour under new manager Jack Ross.
He then played 22 times as the Diamonds missed out on promotion after losing their play-off semi-final.
Hutton, a former Scotland Under-21 cap who started his career with Rangers, had loan spells with Partick Thistle and Dunfermline Athletic before joining Queen of the South prior to spending a season with St Mirren.
He becomes Dumbarton's second addition this week, with 20-year-old Hearts striker Ally Roy having joined on loan ahead of Tuesday's 3-1 League Cup defeat by Ayr United.
Roy, a product of Hearts' youth system, has had previous loan spells with East Stirlingshire and Stenhousemuir, scoring three goals in 30 appearances for the side relegated from League One last season.
He signed a new two-year contract at Tynecastle this summer and will initially be with Dumbarton until January.
Roy made his debut as a second-half substitute in the defeat by League One side Ayr.
Hutton could make his first appearance in the Sons' next Group E game, away to League Two outfit Clyde on Saturday.
Former Rangers midfielder Kyle Hutton has joined Dumbarton after being released by St Mirren.