John Haggan was born on Constance Street in Belfast, son of Belfast natives Edward Haggan, a seaman, and Mary McGee. John had seven siblings in total and in the late 1890s John joined the Royal Horse Artillery and served during the Boer War, he even participated in the funeral procession of Queen Victoria in 1901. 

John initially signed-on to the Titanic in Belfast for the delivery trip to Southampton. He then signed on from Southampton to do the Atlantic crossing, for this trip he gave his address as the Sailor's Home, Southampton. 

Haggan would survive the sinking,  probably on lifeboat 3, and he returned to England onboard Lapland. He was not called to give evidence to either the British or US inquiry.  

He never liked to discuss the disaster and remained in Belfast. He never married and died in Belfast Royal Victoria Hospital in January 1952  after heart failure and pneumonia. He was buried in the family plot with his parents and several siblings in Dundonald Cemetery, Dundonald, Co. Down,