The Spanish defender joins from Celta Vigo on a free transfer and becomes new Manager Pierre Sage’s first signing of the summer.
A versatile operator, Mingueza can play anywhere across the backline.
The 27-year-old Spain international has won four caps at senior level, starting for La Roja in the 2025 UEFA Nations League final.
Born in Catalonia, Mingueza came through the ranks at Barcelona’s prestigious La Masia academy.
He made his senior debut for the club in 2020, winning the Copa del Rey a year later and went on to make 66 appearances before moving to Celta Vigo in 2022.
Mingueza boasts plenty of European experience and was named in the UEFA Europa League Team of the Season in 2025/26 after helping Celta Vigo reach the quarter-finals.
Chairman Steve Parish said: “We are delighted to welcome a player of Óscar's quality and character to the club.
“His track record speaks for itself, with experience at the highest level for both club and country.
“We believe he will be a fantastic fit for Crystal Palace.”
Mingueza said: “I’m really excited to be here. It’s an honour to join Crystal Palace and I can’t wait to see you at Selhurst Park.”
Everyone at Palace would like to welcome Óscar to South London and wish him the very best for his career in red and blue.