 McEwen attended state schools in Wangaratta and Dandenong until the age of thirteen, when he began working for Rocke, Tompsitt & Co., a drug manufacturer in central Melbourne.He initially worked as a switchboard operator, for which he was paid 15 shillings per week.McEwen began attending night school in Prahran, and in 1915 passed an examination for the Commonwealth Public Service and began working as a junior clerk at the office of the Commonwealth Crown Solicitor.