The tee shot at the par-three 15th by Block, one of 20 teaching professionals in the field at Oak Hill, soared into the air and then slammed straight into the cup without even rattling the flagstick.
The moment left Block, who was playing in a group with four-time major winner Rory McIlroy, in disbelief.
"No, no, no way. Rory did it go in?" Block said on the tee as spectators erupted in wild scenes around the green.
It marked the first hole-in-one at the PGA Championship since 2020 when South Korean An Byeong-hun aced the 11th hole during the final round at TPC Harding Park in San Francisco.
The last club professional to hit a hole-in-one at a PGA Championship was George Bowman, who aced the third hole in his first round at Valhalla Golf Club in 1996.
