Boxhall followed in the footsteps of his ancestors on 2 June 1899, when he joined his first ship, a barque of the William Thomas Line of Liverpool. Boxhall's apprenticeship lasted four years, during which time he travelled extensively. He then went to work with his father at Wilson Line and, after obtaining his Master's and Extra-Master's certifications in September 1907, joined the White Star Line. He served on White Star's liners Oceanic and Arabic before moving to the Titanic as Fourth Officer in 1912; he was then 28 years old.
When Titanic collided with an iceberg at 11.40 PM on 14 April, Officer Boxhall was off duty near the Officers' Quarters. Hearing the lookout bell, he headed immediately to the bridge, arriving just after the impact. Capt. Smith, who had also just arrived on the bridge, ordered Boxhall to perform an inspection of the forward part of the ship. He found no damage, but was later intercepted by the ship's carpenter, who informed him that the ship was taking water. A mail clerk confirmed this to Boxhall and Captain Smith. Later, it was Boxhall who calculated the Titanic's position so that a distress signal could be sent out. It was also Boxhall who sighted the masthead lights of a nearby vessel (possibly the SS Californian) and attempted in vain to signal by Morse lamp and distress flares.
Officer Boxhall was put in charge of lifeboat No. 2, which was lowered from the port side at 1.45 AM with 18 persons aboard out of a possible 40. He rowed away from the ship for fear of being pulled down by suction. Boxhall did not actually see the Titanic founder, as her lights had gone off and his lifeboat was about three-quarters of a mile distant. Boxhall spotted the Carpathia on the horizon at 4.00 AM and guided her to the lifeboats with a green flare. After being collected by the Carpathia, Boxhall and the other survivors arrived at Pier 54 in New York on 18 April.
While in New York, he served as a witness in the American inquiry into the sinking. He and his fellow surviving officers were allowed to leave New York on the Adriatic on 2 May. After returning to England, Boxhall bore witness again, this time at the British inquiry. Much of his testimony concerned details of the lifeboat lowerings and Titanic's navigation, including the many ice warnings. He was also the first person to testify that he saw another vessel in close proximity while Titanic sank.
Boxhall returned to White Star following the war in May 1919, having married Marjory Beddells two months prior. After the White Star-Cunard merger in 1933, he served in senior capacity as first and later chief officer of the RMS Aquitania, although he was never made a captain in the merchant marine. After 41 years at sea, he retired in 1940. Boxhall was a generally taciturn and quiet man, usually reluctant to speak about his experiences on the Titanic. However, in 1958, he acted as a technical advisor for the film adaptation of Walter Lord's documentary-style novel, A Night to Remember, and also gave a BBC interview in 1962.
His health deteriorated sharply in the 1960s, and he was eventually hospitalized; Joseph Boxhall, the last surviving deck officer of Titanic, died of a cerebral thrombosis 25 April 1967. He was 83. According to his last wishes, his ashes were scattered to sea at 41°46N 50°14W – the position he had calculated as Titanic's final resting place over half a century earlier. Ruth Becker and Frank Goldsmith also had their remains scattered over Titanic's final resting place.
Boxhall was portrayed by Gerard Plunkett in the 1996 TV miniseries, Titanic, and inaccurately portrayed as having been lost with the ship.