Parslow served as a junior officer with the 1st Regiment of Foot Guards.

[2] He became colonel of the 70th (Glasgow Lowland) Regiment of Foot in April 1758,[3] colonel of the 54th Regiment of Foot in September 1760[4][5] and colonel of the 30th Regiment of Foot in April 1770.

[8] John Parslow married Margaret Hillersden, the daughter of the Whig MP for Bedford, William Hillersden, and his wife Elizabeth.

[9] Parslow's daughter Charlotte predeceased him on 11 June 1786.

[10] Parslow himself died at the town of Bath on 15 November 1786.