[1][2] Pienaar received his schooling in Somerset West and then went to Victoria College in 1907, where he obtained his degree and teacher's diploma.
In 1915, as captain, Pienaar helped Malmesbury win the Grand Challenge Cup, the club competition in the Western Province and in 1920 and 1921 he was captain of Caledon.
He played for Western Province from 1914 to 1922 and captained them against the combined New Zealand military team of 1919 and then again in the Currie Cup competition in 1920.
[3] In 1921, Pienaar was selected as captain for the Springbok team that undertook a tour to Australia and New Zealand for the first time.
[2] Pienaar became South African Selector in 1928 and served on that committee until 1931 when he was elected Manager of Bennie Osler's Springbok team that toured Britain and Ireland in 1931–32.