Just after 2 a.m. E.T., Fetterman led by more than 2 percentage points with about 93% of expected votes being reported.
Speaking for roughly seven minutes at his election night event in Pittsburgh, Fetterman said: "This race is for the future of every community all across Pennsylvania.
At his party in Bucks County, Oz spoke briefly just before midnight, expressing confidence that he would emerge victorious.
Democrats seized on the response as a sign that Oz believes that the government should be involved in personal health choices.
Mehmet Oz takes part in a forum for Pennsylvania Republican Senate candidates in Camp Hill, Pa., on April 2.
Oz was also dogged by skepticism over his ties to Pennsylvania — after attending the University of Pennsylvania in the 1980s, Oz only moved back to the state in alignment with his Senate bid.
For Fetterman, 50% said he was healthy enough to represent the state while 47% said he was not. »