'It's nice to win a playoff,' said Irwin, who also won this tournament in 1997. 'I still have some goals to attain this year.'
Irwin and McCord finished regulation knotted at 8-under-par 208. The duo returned to the tee at the par-5 18th for the first, and only, extra hole. After McCord drove into the rough, Irwin was in the driver's seat with a clear view of the green.
Irwin carried the water in front of the putting surface with his second shot and his ball landed pin high in the rough. He chipped to eight feet and drained the putt for the win and a $225,000 first-place check.
The all-time winner on the Senior Tour has had tremendous success in Hawaii with his sixth victory in the Aloha State. However, the final round at the Palmer Course at Turtle Bay Resort on Sunday was a highly contested battle.
'I never felt like it was going to be anything but tough all day,' said Irwin, who carded a final-round 70. 'Trying to get through the day was the first order of business.'
Irwin was part of a four-way tie atop the leaderboard after the second round and fought hard to remain afoot as fellow overnight co-leaders Dick Mast, Mike Smith and Morris Hatalsky had intentions of their own.
Mast had the most success early and jumped into the lead with three birdies on the front nine that moved him to 9-under for the tournament. He had a two-shot lead at one point, but came back to the field with a bogey at the 13th.
Irwin was consistent throughout his round and started with a 20-foot birdie at the first. He later hit a 9-iron inside three feet for birdie at the ninth.
'I wasn't doing my thing early,' said Irwin, who secured the top spot in the race for the 2002 Charles Schwab Cup with the win. 'I made some great saves early on. My experience playing on Sunday helped me in the end.'
McCord put himself into the mix with a birdie at the third. Despite a bogey at the following hole, McCord ran home three consecutive birdies starting at the par-4 seventh.
Smith remained near the top of the leaderboard, but finished shy of the playoff after a round of 71. Smith was joined by Mast and John Bland at 7-under-par 209.
Hatalsky collected two birdies and two bogeys to finish alongside Isao Aoki and Steve Veriato at 6-under-par 210.
Sammy Rachels was one shot further back, followed by Andy North, who finished at 4-under-par 212.
Final results from the Turtle Bay Championship