Basham was born in Newport in 1890 and took up boxing in professionally in 1909. A slim-framed man, he was said to have lightning punching power, and became a local and national figure in the boxing world.

His first professional fight against Boxer Ryan on 18 October 1909, was fought at Campbell Bannerman Hall in Newport. The six round fight only lasted until the third when Basham took the match via a knockout. He followed this win with a series of regular contests throughout 1910, mainly taking place in Newport. These were against fighters with limited experience, and his results were patchy, having won three, lost three and drawn one by June 1910, including losing to Fred Dyer, the Singing Boxer on Dyer's debut

He first took the British welterweight title in 1914 a few months after the outbreak of World War I. He had joined the Army in 1912 and as a Royal Welch Fusilier was stationed at the Barracks in Hightown, Wrexham, with many of his fights taking place in the town or in nearby Liverpool.

Whilst the war interfered with his boxing career, he still managed to defend his title in 1915 and 1916, meaning he was awarded the Lonsdale belt outright. During the war Basham was a member of an elite corps of boxers known as the Famous Six who worked as army physical training instructors. The group included Cardiff fighter "Peerless" Jim Driscoll, a British and Commonwealth featherweight champion.

His career took a nasty turn when an opponent, Harry Price, died in the ring and he faced manslaughter charges. He received a lot of public support, but still had to stand trial. Fortunately for him, the magistrate ruled that the fight had been conducted along sporting lines and Basham was acquitted. When the war finished, the boxer resumed his fighting full-time and in 1921 took the British and European middleweight champion titles in a single fight.

Basham held the Middleweight titles for less than five months, losing both to his arch-rival "Kid" Lewis when the two met in October 1921. Again Basham was unable to last the distance, being stopped by technical knockout in the twelfth. Basham never challenged for a title again and he ended his career with a series of loses, being knocked-out by World Champion Mike McTigue and a points loss to fellow Welshman Jerry Shea. Basham came out of retirement in 1929 to face "Kid" Lewis, but for the fourth time he was stopped within the distance. Basham reportedly suffered from "cauliflower ear," or thickening and enlargement of his left ear, in his retirement due to trauma from boxing.

Sean Davies writes "Towards the end of his life he made a programme for BBC Wales alongside Eddie Thomas and Cliff Curvis and, according to the host GV Wynne Jones (Geevers): “Johnny Basham was a sorry figure and almost destitute and, as unfortunately happened, was to die in poverty within a month.” An American blog notes "Sadly, just a week before the tournament, Johnny Basham died, with a huge crowd turning out for the funeral.  Sufficient funds were not available to mark Johnny's grave in a manner befitting such a great champion, and his resting place was marked with a simple wooden cross for forty years. In 1987 a boxing tournament between Newport and its German twinned town Heidenheim helped raise the money for a headstone." Basham died on 8 June 1947