The Swede has signed a one-year deal after a successful trial period with the Dens Park side.
Sow could now line-up against Hearts a week on Friday when the Jam tarts get their league campaign underway at home to Dundee in front of the BBC cameras.
The 30-year-old has been a free agent since his release from Dundee United earlier this summer.
Dundee become the players’ fourth Scottish club having spent some time on loan at Kilmarnock last season.
He is the fifth forward to join the club this summer with Alex Jakubiak, Danny Mullen, Jonathan Afolabi and Nicholas Hamilton all signing.
“I’m delighted to have Osman join the squad,” Dees boss James McPake told the club's official website.
“We have been really impressed with him over his trial period both in training and in games. He offers a different dimension to the other strikers we have in the squad and he will compliment them well.”
“He’s been with the group for three weeks now and we have had the chance to have a really good look at him in terms of quality, fitness and his character.”
Sow’s most successful period was at Hearts, netting 23 goals in 52 appearances, becoming a fans’ favourite before earning a big money move to China in 2016.
Since then he has played in the UAE and been signed twice by current Hearts boss Robbie Neilson, once for MK Dons before he was brought to Tannadice to try and help the club back into the top-flight.