Couples then went out and carded a course record 9-under 61 at Canyon Meadows Golf and Country Club before beating Billy Andrade in a one-hole playoff to take home the winner's share of US$337,500.
"I really wanted to play well and have a shot of winning," said Couples, who finished in a five-way tie for 10th spot at the inaugural Shaw Charity Classic last year. "Obviously last night I didn't think that. I knew I had to come out and have a great, great round, but I never thought I was going to win — ever."
That all changed when Couples chipped in for eagle from the back of the green of the par-5, 18th hole to move into first place overall at 15 under.
"I landed it right where I wanted to," said Couples, whose round of 61 established a career low. "It was going a little fast, but it obviously hit the pin and went in."
Andrade then tapped in a short putt for an eagle on the 18th to card an 8-under 62 to pull into a tie with Couples through three days of competition at the Champions Tour event.
The pair then went back to the 18th tee for the playoff. Andrade went for the green in two and pulled his second shot right of the green and into the stands.
"I laid up with a wedge and then hit a sand wedge from there," said Couples, who chipped his third shot to within a foot of the hole.
After taking a drop, Andrade's third shot came up about 40 feet short of the hole. After Andrade missed his long putt to the left of the hole, Couples tapped in his birdie putt and received a loud ovation from the large crowd surrounding the 18th green.
"I knew that's what he was going to do and I knew he was probably going to make a four," Andrade said. "I'm literally shocked that that putt missed left for birdie. I thought if anything I was going to miss it to the right — that it was going to go right and it didn't. I made a good valiant effort and it didn't go in."
Couples vowed that he'll be back next year to defend his title at Canyon Meadows.
"I would be back even if Billy won the playoff or if I finished 10th," said Couples, who enjoyed playing in front of the large galleries of fans all weekend. "I really do like the tournament."
Steve Lowery shot 64 in the final round to finish in a tie for third place at 13 under with Joe Daley.
"That's surprising they shot that low," said Lowery, who was pleased with his best finish of the season. "I was thinking 63 might have a shot at it, but you never know when someone's going to come out and shoot 61 like that."
Daley started the day in a tie for top spot with Joe Durant and Bob Tway, but fell out of contention after a bogey on the par-3, 16th hole.
"That wind was really blowing on 16 and I happened to run it by a little bit," said Daley, who commended both Couples and Andrade for their outstanding final rounds. "There's certain times when guys are going to do that, when they get it going and they post those numbers on the last day. I've done it in the past myself. My hat's off to those guys. They played well."
Wes Short Jr. finished alone in fifth spot at 12 under after shooting a final round of 64.
Rod Spittle of Niagara Falls, Ont., carded a final round of even par to finish as the low Canadian in a four-way tie for 47th spot at 3 under.
Victoria's Jim Rutledge finished one shot behind Spittle after shooting a 5-under 65, while Calgary's Stephen Ames finished well back after carding a 71.
Calgary's Darryl James shot a respectable 69 on Sunday, but still finished in second last spot at 8 over.