This win moved the Hamilton pro to 20th on the order of merit, which would see him earn direct entry to next year's PGA Tour if he can finish the year inside the top 25.
The 41-year-old made a fast start to his fourth round as he birdied the opening hole before making an eagle on the third to be three under par and in a share of the lead after three holes.
He added another birdie on the fifth hole which saw him claim the outright lead from American Chad Collins who bogeyed the par three in a two-shot swing.
Alker made four straight pars to complete the front nine and made the turn in four-under-par on a tournament total of 21-under.
On the back nine he made a string of pars before a birdie at the par-four 14th brought him back to a share of the lead with four holes to play.
Alker continued his run of pars down the stretch and had a long birdie putt to claim the title on the 18th but couldn't find the bottom of the cup, which sent Alker and Hall to a playoff.
Collins had to finish his third round earlier in the day after inclement weather meant 21 players were left with holes to play in their third round today.
Collins held the lead at the start of the fourth round but finished with a two-under 69 to claim a share of third place.
Alker shot in to contention with a brilliant 10-under 61 yesterday as his bogey-free third round saw him climb 30 spots on the leaderboard on moving day. Prior to that he had opened with rounds of 71 and 64.
US pro Will Wilcox, who eventually finished in a tie for third at 21-under, made an impressive charge today as he fired a 12-under 59 in a round that included 10 birdies and an eagle.
Wilcox's round marked only the fourth time a player had recorded a 59 on the Web.com Tour.
Manawatu pro Tim Wilkinson continued his solid showing on Tour this year as he carded a final round six-under 65 to move to 18-under for the tournament, good for a share of 12th place. The left-hander had only one bogey throughout the tournament
Wilkinson came in to the tournament in seventh spot on the order of merit and this weekend's efforts should solidify his spot in the top 25 players on the money list.
Fellow Kiwi Danny Lee missed the cut.