Harry McShane was born in Glasgow on 7 May 1891. Like his close colleague John Maclean, whom he joined in opposing the First World War, he was a member of the British Socialist Party but, unlike Maclean, he joined the Communist Party of Great Britain (CPGB) in 1922. He was also involved with the Tramp Trust Unlimited, which was formed by Maclean to campaign for a minimum wage, a six-hour day and other socialist policies.
In the 1930s he led a number of hunger marches organised by the the National Unemployed Workers' Movement. In 1953 he left the CPGB over disagreements with its leadership and joined the International Socialists in 1963, remaining a committed socialist until the end of his life. He worked as an engineer until his retirement at the age of 69. He died on 12 April 1988.