The 33-year-old, whose career has been plagued by injury, has not yet discussed a new deal with the club, and feels that is an indication that he will be a free agent in the summer.
"At the moment, it looks like the club is no longer planning with me," he told the Westdeutsche Allgemeine Zeitung newspaper.
"But it is fair enough that they don't go out of their way for a player who has been out injured for a year and is now 33."
Owomoyela's last appearance for Dortmund came just over a year ago, on April 28.
He has since struggled with a calf injury and a stress fracture in his heel, failing with several attempts at a comeback.
Capped 11 times by Germany, Owomoyela - who played for an hour for Dortmund's reserves yesterday - last pulled on his national team's shirt in March 2006.