The 24-year-old Valencian defender's previous deal ran until 2029. The extension adds two years and formally marks his integration into the first-team squad.
Villarreal described him as "one of the best defenders in La Liga" — a verdict supported by a season in which Romero started 36 of Espanyol's league matches and contributed six goals, making him one of the most productive attacking full-backs in the division.
Romero joined Villarreal's academy from local club Torre Levante in 2019, progressing through the youth ranks before establishing himself at Villarreal B and making eight first-team appearances in 2023-24. His loan to Espanyol the following summer allowed him to develop uninterrupted, accumulating 71 La Liga appearances and eight goals across two seasons.
He replaces Alfonso Pedraza, who is leaving the club this summer, reportedly bound for Lazio. Villarreal's other left-back option is Sergi Cardona.
Villarreal finished third in La Liga this season — their highest finish in several years — qualifying for the Champions League group stage. Romero will compete at that level for the first time in 2026-27, adding European football to a career that has been built quietly but convincingly through the Villarreal system.