Head coach Jason Garrett made the announcement Wednesday during his daily news conference.
Sam, 24, the first openly gay player in the league, was cut by the St. Louis Rams Saturday after being taken in the 7th round of the NFL Draft.
The Cowboys could use his help due to injuries on the defense to the likes of Sean Lee, DeMarcus Lawrence and Anthony Spencer, and the loss of marquee players like DeMarcus Ware.
Garrett said Sam will be limited in practice Wednesday. He dodged any questions about tension in the locker room regarding Sam's signing and would only say the team was focused on football and the upcoming regular season opener against the San Francisco 49ers.
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