Alexander signed with the Broncos' practice squad Wednesday, Parker Gabriel of The Denver Post reports.
Alexander is fully healed from an Achilles injury suffered last season and recently worked out for the Falcons and Vikings. The veteran linebacker played nine regular-season games for the Steelers last season, recording 41 combined tackles, 1.0 sacks, an interception and a forced fumble. He'll likely be a candidate to find his way to the 53-man roster once he's up to speed and proves he's in game shape.