Michael Collins, 88, visited Florida's Kennedy Space Center on Tuesday. He marked the precise time - 9.32am - when their rocket took off.
Mr Collins had stayed in lunar orbit while his colleagues Neil Armstrong and Buzz Aldrin walked on the Moon.
Tuesday's meeting kicked off a series of commemorative events across the US.
Mr Collins was the only original member of the three-person crew at the event. Mr Aldrin, 89, did not attend, while Mr Armstrong, who was their commander, died in 2012.
