On 22 August 1998, Mallorca won their first major honor, beating Barcelona in the Supercopa de España. And they did it only one year after promotion from the second division.
Played over two legs, that year's Supercopa was a rematch of the previous season's Copa del Rey final. Barcelona won that one over newly-promoted Mallorca on penalties--1-1 (5-4) after taking the shootout to eight kickers each--but since they also won the league that year, Mallorca qualified for the Supercopa as Copa del Rey runners-up.
The teams met in Mallorca on 18 August for the first leg, where a crowd of 12,000 watched the hosts surrender an early goal, then come back to win 2-1 on an 81st-minute strike from midfielder Jovan Stanković (Stanković had also scored the only goal for Mallorca in the Copa del Rey final).
The return leg saw a substantially larger turnout, as 55,000 passed through the turnstiles at Barcelona's Camp Nou. They were rewarded with a 29th-minute goal from Mallorca striker Dani García, who was starting his first season with Mallorca after transferring from Real Madrid.
It turned out to be the day's only goal, securing the trophy for Mallorca. They returned to the competition in 2003 after winning that year's Copa del Rey final, but finished as runners-up to Real Madrid.