Shortly after joining the 48th Regiment in England in 1821, James Mitchell was sent to New South Wales as assistant surgeon. He arrived on the John Barry in 1821

In 1822 he travelled to Newcastle on the Elizabeth Henrietta where he possibly met with  Helenus and Robert Scott, his future brothers-in-law.  Mitchell was granted 2000 acres of land which he selected at Glendon Brook near Singleton. His property adjoined that of Helenus and Robert Scott.

He did not settle on this land but continued in the capacity of Colonial Surgeon. He further invested in industry around the Newcastle area - and land throughout the Hunter district.

Augusta Maria Scott, sister of Robert, Helenus and Alexander Walker Scott, accompanied her mother to Australia in 1832 and in 1833 she married James Mitchell. Their son, David Scott Mitchell, founder of the Mitchell library, was born in 1836.

He died on 1st February 1869