John Cardwell was born at 13 Hamilton Place in Belfast, Ireland on 8 September 1879. He was the son of William Cardwell, a sailor, and the former Annie Beatty. 

On 16 May 1904 John was married in the Baptist Tabernacle in Knockbreda, Belfast to Jeanette Sterrett (b. 24 June 1880); John was described as a labourer and he and his wife’s address was given as 177 Albertbridge Road, Belfast.  John and Jeanette went on to welcome five sons: Thomas, William, John, David and Joshua. 

By the time of the 1911 census the family were described as Baptists living at 5 Cobham Street in Pottinger in east Belfast. John was by then listed as a steamship fireman.

Prior to Titanic Cardwell had served aboard Cartago. He joined Titanic at Belfast for the delivery trip to Southampton where he then disembarked.
Following the Titanic Cardwell continued to work at sea. 

John Cardwell spent the last two decades of his life living at 81 Holland Drive in Belfast. Widowed in 1945, John himself passed away on 30 October 1963 aged 84 and he was buried with his wife in Dundonald Cemetery, Co Down (plot B3 466).