He won the singles title at the Dutch Tennis Championships in 1912 aged 16 and won the title again in 1915, 1916 and 1917. With Gerard Scheurleer he became doubles champion in 1914, 1915 and with Christiaan van Lennep in 1916 and 1923. Diemer Kool won the national mixed doubles title in 1914, 1916 and 1917.
