He married Katherine, daughter of Alexander Monro, by whom he had three sons—William, George, in the Bombay civil service, and James Achilles.

Afterwards he was resident with Mahadji Scindia at Gwalior, and served on Lord Cornwallis's staff as Persian interpreter in the Third Anglo-Mysore War of 1790–1.

The Nepalese sought the support of the East India Company, Cornwallis offered to mediate, and Kirkpatrick was sent on a mission to meet the Nepal's envoys at Patna.

They went on to Nayakote, where the rulers of Nepal held court, and the British officers of the mission were the first to visit what was then an unknown mountain country.

In a despatch dated 10 January 1802, Wellesley declared himself indebted to Kirkpatrick for help against Tipu Sultan.

[1] Kirkpatrick was appointed one of the commissioners for the partition of Mysore after the fall of Seringapatam, for which he received a sum of ten thousand pagodas.

[1] Kirkpatrick wrote Grammar of the Hindoo Dialect and an Arabic and Persian Vocabulary (1782), published with East India Company support.