Striker Paul Heffernan has joined Dundee, his third Scottish club after spells at Kilmarnock and Hibernian.
The 33-year-old Irishman scored five goals in 30 league matches for the Easter Road side after joining them from Kilmarnock in August 2013.
Dundee manager Paul Hartley has also brought in defender Ben Priest from Wolverhampton Wanderers.
And Stephen McGinn's loan move to Dundee from Sheffield United has become a permanent deal.
McGinn, who had initially joined the Dark Blues until the end of the season, was subsequently released from his Blades contract.
The 26-year-old made his Dundee debut in Saturday's 1-1 draw with Hamilton Academical.
Meanwhile, three players have moved out of Dens Park on loan.
Canada Under-20 international Dylan Carreiro has rejoined League Two leaders Arbroath, the club at which the midfielder spent two months on loan towards the end of last year, scoring five goals in 11 games.
And 20-year-old winger Phil Roberts has moved to Championship outfit Alloa Athletic, who have also signed former Dover Athletic striker Greg Rutherford.
Midfielder Jamie Reid, 21, has moved to Elgin City in League Two having spent the first half of the season on loan to Stenhousemuir in League One.