The fish pathogen Aliivibrio (Vibrio) salmonicida LFI1238 is thought to be incapable of utilizing chitin as a nutrient source, since approximately half of the genes representing the chitinolytic pathway are disrupted by insertion sequences. In the present study, we combined a broad set of analytical methods to investigate this hypothesis. Cultivation studies revealed that A. salmonicida grew efficiently on N-acetylglucosamine (GlcNAc) and chitobiose [(GlcNAc) 2 ], the primary soluble products resulting from enzymatic chitin hydrolysis. The bacterium was also able to grow on chitin particles, albeit at a lower rate than on the soluble substrates. The genome of the bacterium contains five disrupted chitinase genes (pseudogenes) and three intact genes encoding a glycoside hydrolase family 18 (GH18) chitinase and two auxiliary activity family 10 (AA10) lytic polysaccharide monooxygenases (LPMOs). Biochemical characterization showed that the chitinase and LPMOs were able to depolymerize both aand b-chitin to (GlcNAc) 2 and oxidized chitooligosaccharides, respectively. Notably, the chitinase displayed up to 50-fold lower activity than other well-studied chitinases. Deletion of the genes encoding the intact chitinolytic enzymes showed that the chitinase was important for growth on b-chitin, whereas the LPMO gene deletion variants only showed minor growth defects on this substrate. Finally, proteomic analysis of A. salmonicida LFI1238 growth on b-chitin showed expression of all three chitinolytic enzymes and, intriguingly, also three of the disrupted chitinases. In conclusion, our results show that A. salmonicida LFI1238 can utilize chitin as a nutrient source and that the GH18 chitinase and the two LPMOs are needed for this ability.