After Karim Benzema had scored the only goal in Seville in last week's semi-final first leg, Jose Mourinho's side had to deal with some tireless chasing and crunching tackles from a fired up Sevilla before their two German internationals combined to make the vital breakthrough in the 82nd minute.
Sami Khedira's superb pass from central midfield sent Mesut Ozil clear and he rounded goalkeeper Javi Varas to finish into the empty net.
"We do not want to speculate about the result," Mourinho said at a news conference when asked about his predictions for the April 20 final.
"History shows that there are never any favourites in finals," the Portuguese added. "It's better to be in a final than not and we deserve to be there."
The final, which has yet to be given a venue, takes place a few days after the great rivals meet in Madrid in the league and they could also be drawn to play each other home and away in April's Champions League quarter-finals.
Barca coach Pep Guardiola left World Player of the Year Lionel Messi and five Spanish World Cup winners out of his starting 11 at Almeria's Juegos Mediterraneos stadium.
"Getting to the final is very tough," Guardiola told a news conference. "We deserve it and the fact we have been there twice in three years says a lot about our players."
Barca are the record King's Cup winners, with 25 from 34 appearances in the final, a much better record than Real, who have won 17 of 36 finals.
