Nathaniel W. Niles also excelled at tennis, and was inducted into the New England Tennis Hall of Fame in 2000. While a student at Harvard, he was an NCAA champion for the sport. He competed in 23 successive U.S. National Championships. Together with Edith Rotch he won the 1908 Mixed Doubles title and in 1917 he reached the singles final but was defeated by Robert Lindley Murray in four sets. He also reached the semifinals in 1913 and the quarterfinals in 1904, 1911 and 1918.