Legionella pneumophila (Lp) is the causative agent of Legionnaires' disease, an atypical pneumonia. Lp is found in freshwater habitats and replicates within different protozoa (amoebae). It is known that Lp uses amino acids as primary energy and carbon sources for replication. However, very recently it was reported that Lp is able to metabolize also carbohydrates (glucose). Here, we present for the first time experimental evidence that the lpp0489 [gamA] gene encodes a eukaryotic-like glucoamylase (GamA) responsible for the glycogen- and starch-degrading activities of Lp. Although not essential for intra- and extracellular growth, we showed that GamA is expressed and active during intracellular replication in Acanthamoeba castellanii, suggesting that Lp is degrading glycogen during intracellular replication. Altogether, these findings indicate that Lp is indeed able to degrade exogenous polysaccharides and to utilize carbohydrates (glucose).