Terms of the deal were not available. Both sides are working on the final language of the contract. The rookie tight end is expected to sign the deal at Lions headquarters.
Pettitgrew was the 20th pick of the first round and the 15th first-round player to strike a deal. The 6-foot-5, 263-pound tight end from Oklahoma was the first player at this position drafted. He is expected to be Detroit's starter this season.
Also Friday, fourth-round pick Sammie Lee Hill, a defensive tackle, was signed to a three-year contract. The team did not disclose terms.
Senior writer John Clayton covers the NFL for ESPN.com.