Ken Roosa told Utah media the celebrity doctor dashed to his aid Saturday after Roosa collapsed just after a 5K race in Salt Lake City.
Race footage shows Oz, who emceed the event and was dressed in a red superhero cape, kneeling on the pavement to assist the 53-year-old Ohio man.
Roosa says he wasn't used to distance running and suffered dehydration and stress. He was hospitalized for 30 hours.
A picture posted on Oz's Facebook Saturday shows him at Roosa's hospital bedside.
On Tuesday, Oz rushed to help a British tourist struck by a cab in New York City.