Two strokes behind Stricker with three holes to play, Lehman closed with two birdies and a par for a 7-under 66 and a one-stroke victory over playing partner Stricker. The 58-year-old Lehman is coming off arthroscopic surgery on his right knee.
"I haven't been playing a lot of golf," Lehman said. "Had surgery in early November. Had a great doctor and had a great physical therapist, Tom Bratcher, who kind of really put me through the paces over the last 3 1/2-4 months getting ready to play. I give him a lot the credit.
Stricker followed his second-round 63 with a 70. He was trying to become the 19th player to win in his first start on the 50-and-over tour and first since Miguel Angel Jimenez in 2014.
"It was a good week. It was a good positive week," Stricker said. "I did a lot of good things. My game is always a work in progress, it's like anybody's, and I haven't played that much yet so far this year. I think this is just my fourth event. Yeah, I'm excited."
Stricker bogeyed the par-3 16th, matched Lehman with a birdie on the par-5 17th, and bogeyed the par-4 18th after hitting a 3-wood drive left into the water.
"I clawed my way back and I took a couple-shot lead going up to 16 there," Stricker said. "I three-putt and he makes birdie and that was really the tournament. The drive on the last, which I thought was a good one, it was 300 yards to that water there on that line and I hit 3-wood and we thought we had it into the wind, so I don't know how it went so far."
Lehman won for the first time since the 2015 SAS Championship, finishing at 20-under 199 on Omni Tucson National's Catalina Course. He won the 1996 British Open and four other PGA Tour titles.
"I've been working hard to get in shape. Since I couldn't play golf, I spent a lot of time just trying to get in better shape and I think that really paid off this week. I feel much better over the golf ball, hit a lot of good shots, made some good putts, had a lot of energy."
Stricker turned 50 on Feb. 23. The 12-time PGA Tour winner will captain the U.S. Presidents Cup team in September. He missed the cut last week in the PGA Tour's Valspar Championship.
"He played quite well himself," Lehman said. "He has nothing to be ashamed of. I can assure you, he played outstanding golf and I just made a couple more putts."
Lehman erased a three-stroke deficit on the first two holes, making a birdie and eagle, while Stricker opened with his first bogey of the week.
Bob Estes (67) tied for 23rd at 8 under in his senior debut.