The 26-year-old from Queenstown has gone back to No25 in the world men's doubles rankings.
That follows an impressive display in which he reached the Wimbledon quarterfinals alongside partner Jan-Lennard Struff.
The duo won through three rounds, before falling to Joe Salisbury and Frederik Nielsen.
McLachlan had spent most of May on that same ranking, although hovered at 26th and 27th over the past six weeks.
It continues his rapid rise, which began after his switch to compete for Japan - being eligible through his mother - last year.
After being ranked 141st in mid-September year, he skyrocketed to 80th after winning the Japan Open alongside Yasutaka Uchiyama in October.
He entered 2018 ranked 73rd and then had a dream run to the Australian Open semifinal in his grand slam debut when he partnered Struff for the first time.
From there, he jumped from 73rd to 36th in the world and continued to rise steadily through to the French Open in which he and Struff lost in the first round.
