Cubarsi was instrumental in Spain's World Cup triumph, picking up the FIFA Young Player of the Tournament award. He anchored the Barcelona defence as they won a second consecutive LaLiga title.
The Golden Boy award is decided by votes from journalists and is given to the best young player over a calendar year. Players must be under 21 and play in a top European division to qualify for it.
"I'm very proud to receive the award and I thank all the people that voted for me," Cubarsi said in a video broadcast by Tuttosport at the awards ceremony.
"It's been a spectacular year and we're going for more," Cubarsi added.
The 19-year-old was the first defender to win the award since Dutchman Matthijs de Ligt in 2018 and only the second since its inception in 2003.
"It's harder for defenders to get recognition... we're less in the spotlight," Cubarsi told Reuters.
"Perhaps our work isn't as visible because, at the end of the day, the forwards score lots of goals, provide assists, play a more attractive style of football, are more eye-catching."
En route to winning the World Cup in North America this year, Spain conceded only one goal in the tournament.
Cubarsi followed in the footsteps of Barcelona teammates Lamine Yamal, Gavi and Pedri, who have all won the award since 2021.
Real Madrid and Sweden forward Felicia Schroeder won the Golden Girl award.