In a 10 – 7 victory over the Toronto Blue Jays, Bernie Williams and Jorge Posada of the New York Yankees become the first teammates to hit a home run from both sides of the plate in the same game.

This Day In Baseball

On April 23, 2000 — In a 10 – 7 victory over the Toronto Blue Jays, Bernie Williams and Jorge Posada of the New York Yankees become the first teammates to hit a home run from both sides of the plate in the same game.

Source
Baseball Reference April 23