At age 18 he went to sea for nine years, painting in his spare time. In 1915 he "jumped ship" in New Zealand where he worked for a while, then in Australia, finally settling down in Sydney where he studied painting full-time from 1918 to 1920 at the studio of John S. Watkins (1866–1942), becoming an instructor himself within a year. He worked as cartoonist with Smith's Weekly from 1924 to 1950 when it closed; the last artist still on staff. His jokes mostly centred on what he knew best: horses, ships and drunks.
Though he produced many gag panels for Smith's Weekly, he is best remembered for "Uncle Joe and his Horse Radish", a coloured strip which first appeared January 1951 in Keith Murdoch's Sunday Herald, later Sun-Herald and was carried by other News Limited papers including Adelaide's Sunday Mail. It revolved around the splay-footed racehorse and its owners Joe (Swedish like himself) and his wife Gladys, children Oigle and Doigle, their jockey cousin Manfred and the colourful characters of the racecourse – gamblers, drunks, bookies, nobblers, touts, society belles and so on.
Joe was a big powerful and reckless man with a photographic memory and enormous sense of humour. He also had a huge appetite for alcohol and a fondness for the "great Australian adjective" but it always came out pronounced "bletty". When he was called by Sir John Longstaff "the finest black-and-white artist Australia has produced", Joe's riposte was "Fancy that. And me a bletty Swede too!"
He married Agnes Mary McIntyre in 1927. He died of cardiovascular disease in Sydney in 1963, and was survived by his wife, a son and a daughter.
- Lindesay, Vane (1983). "Jonsson, Nils Josef". Australian Dictionary of Biography. Retrieved 29 June 2010.
- Kerr, Joan (14 November 2007). "Nils Josef Jonsson". Dictionary of Australian Artists Online. Retrieved 29 June 2010.
- Lindesay, Vane (1979). The Inked-In Image. Melbourne: Hutchinson. pp. 45–46. ISBN 0-09-135460-9.
- Ryan, John (1979). Panel By Panel. Sydney: Cassell Australia. p. 73. ISBN 0 7269 7376 9.
- Blaikie, George (1975). Remember Smith's Weekly?. Adelaide: Rigby. pp. 75–79.
- Foyle, Lindsay. "Jonsson, Josef Nils". History of Australian Cartoonists. Australian Cartoonists' Association. Retrieved 29 June 2010.