'They are all special,' said Leonard. 'I think I'll take away from it that I can go out and shoot some low scores, I can come into a week like this and have a chance.'
Overnight leader Davis Love III carded a 3-under 69 but a bogey at the 16th opened the door for Leonard. Love was joined by Chad Campbell in a tie for second at 23-under-par 265.
'Obviously, I'm disappointed with the finish and disappointed with my back nine,' said Love. 'But all in all, a good week and I just didn't hit it or putt as good the last four or five holes as I did the rest of the week.'
Leonard was one shot off the pace of Love to start the final round on the Sunset Course at the Country Club at Mirasol and picked up a quick birdie at the opening hole to reach 20-under.
He still found himself two shots off the pace midway through the front nine, however, after Love made a pair of early birdies.
Leonard grabbed a share of the lead with a birdie at the sixth as Love bogeyed the same hole to complete a two-shot swing. The race for the title was between the two of them from that point on.
'I think combined from a long week, playing in the heat and then kind of realizing that it was going to come down to Davis and I, it got in a little bit of a match-play situation,' said Leonard. 'We realized that it was just the two of us against each other and that's what it came down to.'
At the par-3 eighth, Leonard dropped his tee shot six feet from the hole but Love did him one better. Love knocked his to three feet and after both players converted for birdie, Love regained sole possession of the lead with a remarkable play the par-5 ninth.
After a long drive, Love landed his second shot two feet from the cup. He tapped in for eagle to reach 24-under while Leonard tried to keep pace with a birdie of his own.
The tables turned once again on the back nine and this time it was Leonard who showed a flash of brilliance. His drive landed in the right rough but he managed to hit a terrific approach that stopped within a foot of the hole for a tap-in birdie to tie Love.
The 30-year-old took the lead outright with a three-foot birdie at the 15th and stood two ahead of the field after Love's mistake at the 16th. Love missed the green at 16 and failed to get up and down.
'Coming down the stretch, we were a little bit tired. You don't freewheel it quite as good,' said Love. 'I think that was the difference.'
Leonard coasted down the stretch and secured his first victory of 2003 despite a bogey at the last.
'I'm excited,' said Leonard, who earned $900,000 for the win. 'It's nice to be playing well this time of year and looking forward to a week off and then getting ready for The Players and then Augusta.'
Tim Herron fired an eight-under 64 to finish two shots off the pace at 22-under-par 266. He was followed by Jim Furyk, Notah Begay III and Billy Mayfair at 21-under-par 267.
Chris DiMarco, John Rollins, Brian Gay, Brett Quigley, Jerry Kelly and Woody Austin finished tied for eighth at 20-under-par 268.
Mark Calcavecchia, a two-time winner of this event, was one shot further back in a group at 19-under-par 269.