John McGrogan was born in 1861 in the Carrick Hill area of Belfast, the eldest of three boys.

In 1902 he married his Anne (Hannah) Dougan.

John McGrogan was a merchant seaman for most of his life and spent many years at sea, working as a greaser onboard such ships as the Mauretania, Lusitania and the Olympic before joining Titanic in 1912 for the delivery trip from Belfast to Southampton.

McGrogan may have intended to continue on the Titanic to New York but on Wednesday, 10th April 1912 from Southampton but John McGrogan was nowhere to be found.  The story goes that while on shore leave in Southampton, John and another man had a few drinks too many and ended so drunk that they missed the Titanic's sailing to Cherbourg.  It is claimed that John and his friend attempted to catch the Titanic by taking a train to Fishguard and then a boat from there to Rosslare and then a train on down to Queenstown to try and catch the Titanic but were a day too late. Low on funds, they then made their way to Dublin and hence back to Belfast, unaware that Titanic had gone down. Back in Belfast, the news had come through about the disaster and John's whole family believed that he had lost his life on Titanic.   

McGrogan does not appear in the list of signed-on crew that failed to join the ship so it is unlikely that he was ever expected to join the Titanic on 10 April, although that may have been his original intention.

John McGrogan would later rejoin Titanic's sister ship Olympic.

He served during World War I and died in 1933. He is buried at Miltown Cemetery, Belfast.