On June 24, 2008, during a game between the Colorado Rockies and the Kansas City Royals, O'Nora was accidentally struck in the head by a fragment from Miguel Olivo's broken bat.

[4] On September 7, 2018, O'Nora was struck in the mask by a foul ball while working the plate as the Boston Red Sox hosted the Houston Astros; he finished the half-inning and then left the game.

[5] On June 15, 2019, O'Nora was struck in the groin by a foul ball while behind the plate during a game between the New York Mets and the St. Louis Cardinals.

After Toronto Blue Jays manager John Gibbons elected to challenge a safe call made by first base umpire Fieldin Culbreth, O'Nora upheld the ruling following a video review that lasted 2 minutes and 34 seconds.

[11] In December 2020, he was arrested and charged with solicitation and possessing criminal tools in connection with a human trafficking sting in Liberty Township, Ohio.