Toledo had a one-stroke lead over Langer and three others heading into the final round of the Greater Gwinnett Championship, and said holding off his idol and others in the final round "is possibly the greatest challenge I've ever had."
Toledo, from Mexicali, Mexico, completed his first-round 68 early Saturday before shooting a 2-under 70 in the second round. Langer had a 66 that left him in a four-way tie for second.
"I've never played against Bernhard," said Toledo, making his seventh career start on the 50-and-over tour. "I think he's a hell of a player.
Langer was tied with Roger Chapman, Tom Pernice Jr. and Mark Calcavecchia. Chapman and Pernice shot 68s, and Calcavecchia had a 71.
Toledo's only win as a professional came in 2005 on the Web.com Tour. He tied for sixth at the Champions Tour's Toshiba Classic this year but said he has never led entering the final round.
Toledo said winning on the senior circuit would "mean everything."
"I'm not afraid to win," he said.
"I grew up in Mexico with nothing," he said. "It would be an unbelievable story for my country."
Michael Allen took the first-round lead by completing a 67 early Saturday.
Allen added another double bogey on No. 5. "That one really (ticked) me off," he said. He recovered for a 73 that left him 4 under and two strokes behind the leader.
Allen said he didn't realize the pine cones were partially in the ground until he pushed them aside and saw "a little bit of a divot in there.
"I thought I probably shouldn't have done that," he said.
Even though the two-stroke penalty matched the deficit he must make up in the final round, Allen said he didn't regret reporting his mistake.
"That's kind of the basis of our game," Allen said. "It's kind of unique. Our game is about integrity, about following the rules. ... There's no reason to cheat, and if I have to cheat to win, I don't want to win."
Langer applauded Allen's decision.
"It only happens in the game of golf," Langer said. "That's what sets us apart. In no other sport will you hear the player say 'Oh, I kicked the other guy. Give me the yellow card.'"
Gene Sauers shot 68 and was tied with Allen at 4 under.
It was a long day for the 55-year-old Langer. He played 24 holes, including six holes early in the morning to complete his first-round 73 following a four-hour rain delay Friday.
Langer, the tour's points leader, had his streak of 21 straight rounds of par or better end with his 73 in the first round. The streak began at the end of last season and included his first five tournaments this year.
"I don't pay attention to that kind of stuff," Langer said. "I'm here to win tournaments and play the best I can."
Langer said it was difficult to refocus this week after a disappointing finish in the Masters last week. He was within two strokes of the lead in the final round before a poor finish on the back nine left him with a final-round 76.
"It was tough," said Langer, a two-time Masters champion. "It was a tough finish for me on Sunday and very difficult Sunday night and Monday. You replay the tape and what I did and the breaks I got and all that stuff. I really didn't play all that bad. It was just the breaks were against me.
"It was fun being in contention. I take a lot of good away from that tournament because I played well for three and a half rounds. It was just the last nine I was very aggressive and I just paid the price."
Langer said his knees also paid the price.
"Right now I'm pretty tired," he said. "My knees are aching because of all these hills. I've been struggling with my knees for about a year and a half and I'm paying the price on these hills. As I said, two weeks in a row on a course like this. I'm looking forward to next week where it's nice and flat."
Langer's three-week tour of Georgia continues at the Liberty Mutual Insurance Legends of Golf in Savannah.
Olin Brown, who was 5 over through 15 holes on Friday, withdrew with a back injury. Gene Jones was disqualified after opening with a 73 but failing to make his tee time for the second round.