Hailing from Queenstown but now playing for Japan, McLachlan and British player Luke Bambridge have beaten New Zealand's Marcus Daniell and his Austrian partner Philipp Oswald in straight sets in Saturday's final in Auckland.
The Japanese-British combination were 7-6 (3) 6-3 winners on centre-court.
McLachlan, who has a Japanese mother, won the doubles title at the event last year playing with Germany's Jan-Lennard-Struff.
Daniell was unable to pick up his second ASB Classic doubles title, having lifted the trophy back in 2010 with Romanian Horia Tecau.
The doubles final is being followed by the singles title decider.
That match will crown the tournament's first men's singles champion from France, with fifth seed Benoit Paire facing 21-year-old rising prospect Ugo Humbert.
