The St. Louis Blues traded the veteran forward to the Thrashers for Glen Metropolit, first-and third-round picks in this year's draft and a second-round choice in 2008.
If Atlanta re-signs Tkachuk, the Blues will also acquire a first-round draft choice in 2008.
Tkachuk is due to become an unrestricted free agent July 1.
In 61 games this season, Tkachuk has 21 goals and 23 assists.
Metropolit has recorded 12 goals and 16 assists in 57 games with the Thrashers this season.
The NHL's trade deadline is Tuesday at 3 p.m. ET.