Loog Oldham's father, Andrew Loog, was a United States Army Air Forces lieutenant, a Texan of Dutch descent, who served with the Eighth Air Force. Loog was killed in June 1943 when his B-17 bomber was shot down over the English Channel, and he was buried at the Ardennes American Cemetery and Memorial in Belgium. Oldham's Australian mother, Celia Oldham, was a nurse and comptometer operator. Loog Oldham attended the Aylesbury School for Boys, Cokethorpe School in Oxfordshire, St Marylebone Grammar School and Wellingborough School in Northamptonshire.
A self-proclaimed hustler, Loog Oldham spent teenage summers swindling tourists in French towns. His interest in the pop culture of the 1960s and the Soho coffeehouse scene led to working for Carnaby Street mod designer John Stephen and later as an assistant to then-emerging fashion designer Mary Quant. Oldham became a publicist for British and American musicians and for producer Joe Meek. Among his projects were stints publicizing both Bob Dylan (on his first UK visit) and the Beatles (for Brian Epstein) in early 1963.