After the war, Warwick Smith returned to his public service career in the Department of Commerce.[2] He was appointed personal assistant to the Department's Secretary, J.F. Murphy, with whom he gained a lot of trade conference experience.[1]
Warwick Smith's first Secretary role was in the Department of Territories (later External Territories), he moved to the Department in 1964, a time when Australia was coming under increasing United Nations pressure to hasten Papua New Guinea's progress towards self-government.[1] Warwick Smith established an unusual departmental structure with no deputy secretaries, which was unlike most Australian Government departments at the time.[3]
On retirement from the public service, Warwick Smith moved away from Canberra, first to Sydney and later to Bowral, working as a consultant in economic and public affairs.[1] In his later years, Warwick Smith suffered from emphysema, which led to his death on 27 December 1999 in a nursing home in Sydney.[1]