With the roster light a linebacker for the season opener because of Nigel Bradham's one-game suspension, the Eagles picked up Alexander after he was waived by Seattle on Saturday.
The 6-foot-2, 233-pound Alexander played in 12 games for the Seahawks last season, mostly on special teams. A fifth-round draft pick, he spent his first two seasons in the NFL with the Chiefs. He played in all 32 games, starting once, but his role was primarily on special teams there, as well.
The Eagles have yet to announce a corresponding roster move. They could cut a linebacker, mostly likely LaRoy Reynolds or Joe Walker, or a player from another position who was the positive side of the roster bubble after Saturday's 53-man roster became official.