The contest required a shootout after both teams failed to score in normal and extra time.
Spanish goalkeeper Unai Simon made two extraordinary saves against Lovro Majer and Bruno Petkovic before Dani Carvajal netted the winning penalty to secure victory.
It is Spain’s maiden Nations League title and their first silverware since their 2012 European Championship success.
The victory ends a run of disappointments in major tournaments, including Euro 2020 and the 2022 World Cup.
Luis de la Fuente, who replaced Luis Enrique as the head coach after the World Cup, has led La Roja to a title in his fourth game in charge.
Spanish midfielder Rodri had further cause to celebrate after adding another winner’s medal to his trophy cabinet in the space of a week.
The Manchester City midfielder scored the decisive goal in the Champions League final against Inter Milan to help the Cityzens achieve the treble, and he was also awarded the man of the match against Croatia last night.
Captain Jordi Alba and keeper Simon dedicated the victory to former manager Enrique, who laid the groundwork for Spain’s resurgence in recent years.
Croatia skipper Luka Modric cut a sad figure after the defeat as his quest for a major trophy with the national team continued.
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