Willie Lenihan introduced the celebrated Arbour Hill boxing style to Olympic competition at the 1948 London Games - a technique defined by a straight stance, hands held high, body turned to show only a side profile, and the chin tucked behind the left shoulder. He won his only national senior title in 1941 at bantamweight and was selected seven years later on the strength of his exceptional ring craft. In London he won his first two bouts before a quarter-final against Giovanni Zuddas of Italy in which he dominated for two and a half rounds before being floored twice and stopped in the final round. Irish officials felt the referee's intervention was premature.
Outside of boxing, Lenihan worked as an electrician for the Electricity Supply Board (ESB) and was also a member of their athletic club. After his retirement from competitive boxing, he served as a trainer to the Royal College of Surgeons boxing teams and produced local radio broadcasts of boxing instructions. In 1952, he moved to Scotland for an engineering job, and had returned to Ireland by 1974 at which time he was a self-employed businessman. He later retired to Ashbourne, Meath where he remained until his death in 2009 at the age of 88