The incident happened Tuesday around 8 a.m. at the Medical Center Station in Bethesda, located just outside the nation's capital.
Surveillance video shows the moment the man walks along the platform with a white cane before falling onto the tracks below.
Bethesda resident Brendan Cawley told ABC7 he then jumped into action and tried to pull the man out, but realized he couldn't do it alone.
Two other men can be seen running down the platform to help lift the man.
"I said, 'We need to get him up now!'" Cawley told ABC7. "And we did."
The men were able to get the man up onto the platform as the headlights from an oncoming train are seen down the tunnel.
Metro officials told WRC-TV the man was taken to the hospital with non-life threatening injuries
Cawley told ABC7 he was just glad to be where he was at the time to help save the man's life.
“I just knew it was something that I needed to do," he said.