'It was awesome out there,' said Slocum. 'It worked out this time, and it really felt good.'
Aaron Baddeley, whose quest for a PGA Tour title will continue on, bogeyed the par-4 18th on Sunday to complete a round of 66 and finish alone in second place at 21-under-par 267.
'Obviously, I'm a little disappointed,' said Baddeley. 'After all, we played great, both of us. And I knew it ended up being the two of us. We both played really good shot for shot.'
Slocum, who held the 54-hole lead at this event in 2002 before finishing four shots off the pace, made the most of another opportunity at Omni Tucson National.
The 30-year-old began the day in a tie for the lead with Baddeley and vaulted out of the gate with four consecutive birdies from the first to start his round.
Baddeley was not ready to concede the tournament just yet and the young Australian collected four birdies over his first five holes to remain even with Slocum at 19 under.
The duo went back and forth throughout the round as Baddeley grabbed the outright lead with a birdie at the eighth. Slocum responded with a birdie at the very next hole and grabbed the lead on his own with a birdie at the par-5 10th.
Baddeley tied Slocum with a birdie at the 11th and regained sole possession of first with a birdie at the par-4 14th.
Like clockwork, Slocum countered and joined Baddeley at 22 under with a birdie at the par-4 16th.
The pair parred the par-3 17th before walking onto the 18th tee. As Baddeley three-putted for a closing bogey, Slocum left with a par and the win.
'It was a slugfest and we were feeding off each other,' said Slocum, who pocketed $540,000 for the win.
Rory Sabbatini fired a 64 to join Harrison Frazar and Mark Hensby in a tie for third place at 18-under-par 270. Per-Ulrik Johansson and Bill Glasson were one shot further back at 17-under-par 271.
Todd Fischer, Tim Clark, Carlos Franco and Mike Heinen shared eighth place at 16-under-par 272.