In an Instagram post he told fans that he chose the number because of playing the video game FIFA in 2005.
He said he created himself with his brother on the game and chose the No.29 and since then it has stuck.
Back in 2021, in an interview with The Athletic, Havertz told the story in detail.
He said: "When I was young I always used to play FIFA or Pro Evolution Soccer with my brother. We always made ourselves in the game. My brother always put No 29 on his shirt.
"When I came to the professional game and Leverkusen asked me what number I wanted to have, I asked them which numbers were free. When they said 29, I said I'd take it because of my brother."