Birthplace:
- Fodderty, Ross-shire

Birthdate:
- 16 February 1837

Nationality:
- Scottish

Height:
- 5 feet 8 ½ inches

Family Background:
- Mackenzie's father was one Forbes Mackenzie, a Deputy Lieutenant of Ross-shire

At Sandhurst:
- No

Foreign Languages:
- French

Career before Halifax:
- Ensign, 20th Foot, 8 February 1856 (purchase)
- to 42nd Highlanders by transfer, 8 October 1856
- to 78th Highlanders by transfer, 23 October 1857
- Lieutenant, 30 April 1858 (non-purchase)
- Adjutant, 2 April 1861; resigned, 16 May 1862
- Captain, 28 July 1863 (non-purchase)

Medals & Awards:
- None

Postings while 1n NS Command:
- Halifax, 9 May 1869 to 22 June 1869
- Saint John, New Brunswick, 22 June 1869 to 3 August 1870
- Halifax, 4 August 1870 to February 1871

Married:
- No

Career after Halifax:
- Brevet Major, 1 October 1877
- Major, 27 March 1878
- retired 27 March 1885

Thomas Mackenzie was the third son of one Forbes Mackenzie (d. 1844), a noted agricultural improver, and a deputy lieutenant of Ross-shire.  Forbes Mackenzie was a great clearer of land "having reclaimed and laid out the great part of Strathpeffer." At Fodderty, "he was the first to apply lime to the land, and to grow wheat north of the Forth. He was the first to import Clydesdale horses and shorthorn cattle into the northern counties, and ... the first to introduce Cheviot sheep into the highlands.”  Forbes' father, and Thomas' grandfather, one Colin Mackenzie of Glack (d. 1801), was a former chaplain with Lord Macleod's Highlanders, later the 71st Highland Light Infantry. The latter had inherited a fortune from his parents, and had bought the estate of Glack in Aberdeenshire. 

After holding a commission in the 20th East Devonshire Regiment and the 42nd Black Watch, Thomas Mackenzie transferred to the 78th, the regiment most closely identified with his native county. After coming to Halifax with the 78th, Mackenzie was, on 29 June posted with a detachment from the regiment to Saint John, New Brunswick, where he remained until 3 August of the next year. By 18 February 1871 he had left Halifax for Scotland, never to return. He apparently stayed away from the regiment without leave.