The Queenstown doubles specialist and partner Jan-Lennard Struff overcame a strong challenge to beat Lukasz Kubot and Horacio Zeballos 7-6, 2-6, 10-7 yesterday in Auckland.
They finished the stronger of the duos in the match tiebreaker, winning a crucial break point with the score at 7-6.
From there a Struff serve proved too much to return, before McLachlan ended the match with a smash that could not be returned.
It was McLachlan's first appearance in the main draw of the event, his rise in the rankings in the past year helping him gain entry.
He now plays with the Japanese flag next to his name, although he remained popular with the Auckland crowd.
McLachlan/Struff had the upper hand throughout the first set, although had to go to a tiebreak to clinch it.
They looked the more likely to get a break and on three occasions forced Kubot/
Zeballos to deuce.
However, all three times they were unable to finish the game off.
On their own serve they controlled the set, as Kubot and Zeballos struggled to win points, let alone force a break.
That boded well for the tiebreak and while both sides managed two breaks along the way, a McLachlan backhand finished off the winning rally.
It was a different story in the second set and with the score at 2-2, McLachlan and Struff were broken on each of their next two serves to be downed 6-2.
That left them to finish with a match tiebreak and after jumping out to a 4-1 lead, they lost five of the next six points to trail 5-6.
However, they rallied off the McLachlan serve and after Struff forced a break, they were able to play out for the win.
