In the 1946 New Year Honours, Ainsworth was appointed a Knight Bachelor (Kt) in recognition of his role as Director of Medical Services of the Joint War Organization.[13] On 12 March 1946, he was knighted by King George VI during a ceremony at Buckingham Palace.[14] On 23 December 1946, he was promoted to Knight of the Venerable Order of St John (KStJ).[15]