The 27-year-old former Arsenal defender is manager Pierre Sage's second summer signing, following the arrival of defender Oscar Mingueza. Tomiyasu, who can play both as a full-back and a central defender, spent the second half of last season on loan at Dutch club Ajax Amsterdam. He has earned 46 caps for the Japanese national team and was part of their squad for the 2026 World Cup.
Crystal Palace is enjoying a successful period, having won the FA Cup, Community Shield, and the UEFA Europa Conference League over the past two seasons under former manager Oliver Glasner.
"I'm excited to get started. The club is in a very good period, having won three trophies in two seasons. This is exactly where I wanted to be," Tomiyasu stated, according to AFP. Club chairman Steve Parish highlighted his experience: "He has gained experience at the highest level of European and international football. We are delighted to welcome a player of his quality to the club."