He tied the world record for 60-Meter high hurdles of 7.5 seconds at an Olympic trial heat at Madison Square Garden in early 1936. Green was considered sure to make the team in 1936, but chose not to participate. He protested the event being held in Berlin, center of Nazi Germany.
Although Green remained a world class hurdler for many years, he was convinced by his Rabbi to Boycott the Olympic Games based on what was happening in Nazi Germany. The boycott by Milton Green and Harvard teammate Norman Cahners was not publicized at the time.
Green had this to say on an interview transcribed by the US Holocaust Museum. "Both Cahners and I decided that we would boycott the Olympics. We just felt it was the right thing to do. I spoke to the track coach at Harvard. We told him about our intention. He tried to persuade us not to do it. He said he didn't think it would do much good, and we should try to go to the final tryouts and try to make the team. But we didn't want to do that. After we boycotted the Olympics, no one came to speak to us or ask us if we'd make any statements about it. And I don't think anyone knew particularly that we did boycott it. I think back on making that decision and whether I would have won silver or gold or some sort of a medal, and every time I go to the Olympics — I've been to three of them — I particularly watch the high hurdles and the long jump, and I picture myself as maybe having won a medal in it."