Claudia Pina's second-half brace, either side of a Vicky Lopez strike, secured 2023 World Cup winners Spain a third international trophy.
A record crowd on home soil for Spain of 55,843 at Atletico Madrid's Metropolitano Stadium watched Sonia Bermudez's side claim the first silverware of the new coach's reign.
Spain were shorn of three-time Ballon d'Or winner Aitana Bonmati after she fractured her leg on Sunday in training, but swept to victory with a convincing display in the capital.
The Euro 2025 runners-up relied on goalkeeper Cata Coll to keep their hopes alive during the first leg in Kaiserslautern but dominated Christian Wueck's visitors in the decisive second leg.
"We had one objective, which was to win, and we did it," Pina told TVE.
"It was a great game from the whole team and a new trophy," she continued.
"(The atmosphere was) crazy, the fans, who always support us, came here, without them the victory wouldn't have been possible."
Esther Gonzalez fired narrowly wide early on and Ann-Katrin Berger saved Alexia Putellas's header.
Coll fielded two Germany efforts from distance, but Spain were in control.
Arsenal playmaker Mariona Caldentey could have scored twice in the first half, but volleyed over when well placed and punted another effort straight at Berger.
The best chance of the first half fell to Germany's Nicole Anyomi just before the break, but she dragged her shot narrowly wide.
The visitors started the second half strongly, too, before Pina fired Spain ahead in the 61st minute.
The Barcelona forward exchanged passes with Caldentey before drilling home from the edge of the box. Berger got a hand to her shot and could have kept it out.
Her teenage Barça team-mate Lopez grabbed the second with a delicious curling shot past Berger seven minutes later, having come close with a similar effort in the first half which dipped just over.
Pina wrapped up Spain's triumph with a fine solo goal, winning the ball back just inside German territory, driving forward and firing spectacularly into the top corner from distance.
'Proud' Hermoso
Former Atletico and Barcelona striker Jenni Hermoso played the final 10 minutes as a substitute and was overjoyed to win another trophy with the national team.
Hermoso was forcibly kissed on the lips after Spain won the 2023 World Cup by then Spanish football federation president Luis Rubiales, creating worldwide outrage.
Former Spain coach Montse Tome dropped her from the squad but Bermudez recalled Hermoso for the Nations League semis and final after a year in the cold.
"My happy face says it all, to come back, to win in my city, with my people, with the whole family, that we put on a show, it's great," Hermoso told TVE.
"Today I am very proud to wear this shirt, to win a title, and still be enjoying football."