A backrow forward, Johnstone represented Ashburton County and at a provincial level, and was a member of the New Zealand national side, the All Blacks, from 1949 to 1951.
A backrow forward, Johnstone represented Ashburton County while serving in the army The Encyclopedia of New Zealand Rugby, p.105 and later at a provincial level. He was a member of the New Zealand national side, the All Blacks, from 1949 to 1951.