Leandro Calm, the mayor of the city, founded the club as Unión Deportiva Llagostera on November 13, 1947. He also became its first president. Llagostera spent most of its history in the Catalan regional leagues, promoting to Tercera Divisiónfor the first time ahead of the 2009–10 season. In only its second season at that level, the club won its group before defeating CCD Cerceda 3–0 on aggregate in the promotion play-offs. In 2011–12, its first season in Segunda División B, Llagostera finished only one point out of the play-offs, instead qualifying for the next season's Copa del Rey, where it reached the last 32 before a 5–1 aggregate loss to giants Valencia CF. The team was promoted to the professional leagues for the first time in 2014 with a 3–2 aggregate comeback win over Real Avilés and beating Gimnàstic de Tarragona after the overtime in the last round of the playoffs. As their stadium did not meet LFP criteria for home games, Llagostera had as its home stadium from 2014 to 2017 the Estadi Palamós Costa Brava, 30 km from Llagostera, which holds 3,724 spectators. The club held its own in its first season in Segunda División, coming within four points of a play-off berth. It was relegated back to the third tier towards after two seasons. On 30 June 2017, the club announced it would come back to the Estadi Municipal de Llagostera. One year later, Llagostera would be relegated to Tercera División, after losing the relegation playoffs against Izarra, but bounced back immediately with victory against Club Portugalete in June 2019.
