Wirtz had grown up in a family that refused to compromise his development, nor that of his sister Juliane, who plays for Werder Bremen. His father Hans remains the chairman of Grun-Weiss Brauweiler, Wirtz's childhood was framed around the local football team. He grew up with a ball attached to his feet.

The 22-year-old registered 16 goals and 15 assists across 45 games in 2024-25, as Leverkusen finished second in the Bundesliga.