Saints spokesman Greg Bensel says the club re-signed Betts on Wednesday, two days after running back Reggie Bush broke his right leg during New Orleans' victory Monday night at San Francisco.
Betts, who played eight years for Washington, is trying to come back from a serious left knee injury last season. He played in two preseason games with the Saints, rushing nine times for 53 yards and making five catches for 24 yards.
The Saints also waived reserve running back and special teams player DeShawn Wynn. Wynn is eligible for the practice squad and could be re-signed if he clears waivers.
Bush hurt himself after recovering his muffed punt with 6:58 remaining. He had trouble catching the ball at windy Candlestick Park and was hurt diving to cover up the loose ball.
"Last second it kind of shifted a little bit, just enough for me to drop it," he said. "I tried to recover it and somebody took my leg out. I don't know who it was, what happened or how it happened. I just know my leg got taken out. That's it."
The injury is not expected to end Bush's season, sources told ESPN NFL Insider Adam Schefter, indicating he could return in four to six weeks.
The Saints have yet to give an update on Bush's prognosis.
Information from The Associated Press was used in this report.