The Rams on Thursday agreed to terms with free-agent running back Lance Dunbar, a person with knowledge of the situation said.
Dunbar, 27, met with the Rams on Wednesday.
The Rams were seeking another backup for Todd Gurley, the 2015 NFL offensive rookie of the year who is expected to rebound from a disappointing performance last season.
Benny Cunningham was Gurley's backup in 2016, but he was placed on injured reserve for the last three games because of a neck injury. Cunningham, who also returned kickoffs, is a free agent.
Dunbar rushed for 422 yards in 94 carries in five seasons with the Dallas Cowboys.
Last season, playing behind rookie Ezekiel Elliott, Dunbar carried only nine times for 31 yards. He caught 16 passes. In 2015, he had five carries for 67 yards and caught 21 passes.
Dunbar joins a Rams running back corps that also includes Malcolm Brown and Aaron Green. Free agent Chase Reynolds is listed as a running back but mainly plays on special teams.
Dunbar originally signed with the Cowboys as an undrafted free agent after playing in college at North Texas.
Dunbar is the fourth free agent to join the Rams this offseason, joining receiver Robert Woods, offensive tackle Andrew Whitworth and cornerback Kayvon Webster.
The Rams gave center Ryan Groy a two-year offer sheet, and they are waiting to find out if the Buffalo Bills match it to keep Groy.