Ferrier was playing to a handicap of scratch (zero) by his mid-teens, when he left school to be able to play more golf; he was club champion for the first time at Manly at age 15. His first significant win at the state level came in the 1931 New South Wales Amateur Championship, and he repeated there in 1934, 1937, and 1938. From age 16, Ferrier represented New South Wales seven times in Australian men's inter-state team play, in 1931, 1933, 1934, 1935, 1936, 1937, and 1939; he compiled an overall head-to-head record of 7 wins and 3 losses in those events. He also played for New South Wales in the 1932 Kirk-Windeyer Cup, winning all his matches.
He was runner-up in the 1931 Australian Open at the age of 16, taking a six on the 72nd hole to lose by one stroke to five-time champion Ivo Whitton. He also finished runner-up in that championship in 1933 and 1935. He broke through to win in both 1938 (by 14 strokes) and 1939, still as an amateur. He won the Australian Amateur title in 1935, 1936, 1938 and 1939; his four titles in that event is tied for most with Michael Scott. Ferrier was also victorious in eight further significant Australian professional Open events during the 1930s (see below).