Advocate. Son of John Mackenzie and Rebecca Mackenzie. Married (1763 or 1769) to Maria Lancaster, daughter of John Lancaster of Cambridge. They had 6 children. Sometime Commissary of Edinburgh. At the time of his death in 1774, Mackenzie was Sheriff-depute of Ross and Cromarty.
Boswell met Mackenzie at Kames on October 24, 1762, describing him as "a young gentleman of Inverness-shire, very genteel and well-bred and obliging".