Atogwe, who turns 31 on Saturday, spent last season with Washington after playing his first six seasons in St. Louis. The move was announced Wednesday.
Atogwe was a third-round pick in 2005 out of Stanford. He has 520 tackles, 25 interceptions, 5.5 sacks and 19 forced fumbles.
Atogwe provides depth behind starters Nate Allen and Nate Coleman, though he could compete for a starting spot in training camp.