The signing, first announced by Vobora's agent on Twitter, has been confirmed with the team by 710 ESPN Seattle's Liz Mathews. Terms of the deal were not disclosed. To make room on the roster, the Seahawks released running back Vai Taua, who had signed with the team on Aug. 14.
Vobora, 25, started 16 games in three seasons for St. Louis. He started five of 14 games last season, making 36 tackles and two sacks. He played at Idaho and was "Mr. Irrelevant" – the title given to the last player taken in the draft – in 2008.
The Rams released Vobora earlier this month after adding former Vikings linebacker Ben Leber, whom the Seahawks reportedly were interested in.
In January, Vobora was awarded $5.4 million in a lawsuit against a supplement company after using its "Ultimate Sports Spray," which Vobora said he didn't know contained a banned substance. Vobora failed a drug test in 2009 and was suspended four games.