Sabbatini, who shot a 72 on Thursday, hit an iron onto the green. His neon yellow ball bounced twice and fell into the hole.
"I just hit as high a 5-iron as I could up in the air with a high cut," Sabbatini said. "Landed, one bounce into the hole. That's what I was told. I'm not sure exactly. I'm not that tall, so I can't really see over the bunker that well."
Sabbatini became the first Slovakian to sink an ace in the U.S. Open. It was the eighth hole-in-one ever in the U.S. Open at Pebble Beach, and the 45th in tournament history. Zach Johnson previously had the last ace at the event, coming on the ninth hole at Pinehurst in 2014.
There have only been three aces at Pebble Peach since the 1982 U.S. Open. Before Sabbatini, Thongchai Kaidee made a hole-in-one on the fifth hole during the third round in 2010. Todd Fischer made one in 2000.
Sabbatini had two birdies and five bogeys in the first round. He finished 1-over par.