Abecassis was born to American parents who settled in London in the 1890s. His father was of Portuguese-Jewish origin. He himself spent years of his youth in California where his parents resettled after Great Britain was hit by an economic crisis as a result of the First World War.
In 1935 Abecassis began his career in the British racing scene, which focused on races in Brooklands and Donington Park and operated largely independently of European motorsport.
After the Second World War , which he completed as a pilot in the Royal Air Force , he founded the HWM automobile company together with John Heath and competed in numerous races on Alta , ERA and, from 1950, on HWM. Abecassis was also active in the sports car sector, especially on Aston Martin . His greatest successes included class wins at the Le Mans 24-hour race and the Sebring 12-hour race . In Formula 1 , however, he was rarely seen, but in two world championship races ( Swiss Grand Prix in 1951 and 1952) he never crossed the finish line. Numerous other sports car races followed on an HWM Jaguar sports car, and he celebrated several victories at local races in Great Britain.
After the accidental death of his partner John Heath at the Mille Miglia in 1956 , Abecassis lost interest in racing. He also worked as an importer of Facel Vega vehicles from France.
In 1956 he married Angela Brown (1932-2000), the daughter of (Sir) David Brown (1904-93), who was the owner of Aston Martin from 1947 to 1972 . His son David Abecassis published an extensive biography of his father in 2010 under the title " A Passion for Speed ".