Milton Green equaled the World indoor record in the 45-Yard High Hurdles four times in 1935 and 1936 and matched the World indoor mark in the 60-Meter High Hurdles in 1936. But even though he was one of the premier American collegiate track stars of the era, he nonetheless refused to be considered for the 1936 Olympics in support of the U.S. movement to boycott the Nazi Games.

Running for Harvard University, Green first equaled the World indoor mark of 5.8 seconds in the 45-Yard High Hurdles in a January 13, 1935, triangular meet against Yale and Princeton. Two weeks later, on January 27, in a Knights of Columbus meet at the Boston Garden, he matched the record twice in the same event—first in a qualifying heat and again en route to winning the race. Thirteen months later, now Harvard track and field team captain, Green once again tied the World indoor 45-Yard High Hurdle mark in a quadrangular meeting against Yale, Dartmouth, and Cornell. His world indoor record tying performance (7.5 seconds) in the 60-Meter High Hurdles came in a qualifying heat at the 1936 Millrose Games in New York’s Madison Square Garden.

Green was invited to the U.S. Olympic Team's final qualifying meet at Randall's Island, New York, in 1936 and was considered certain to make the team. Rabbi Levy, his rabbi at the Reform Temple in Boston, requested that Green and Harvard teammate Norman Cahners boycott the U.S. Olympic Trials, "to make a statement about participating in Berlin at the time the Nazi atrocities were coming to light." Both Harvard track stars decided to boycott the Olympics because they felt it was the right thing to do.

Green set many collegiate records in the high and low hurdles and long jump events and was elected to the Harvard Athletic Hall of Fame in 1961.