Abstract Background Limited information is available on electrolyte abnormalities in cats with chronic inflammatory enteropathy (CIE). Hypothesis/Objectives Report the prevalence of electrolyte abnormalities in cats with CIE compared to other gastrointestinal disorders, and determine their association with disease and outcome variables in cats with CIE. Animals Three hundred twenty-eight client-owned cats from 2 referral hospitals: CIE (132), alimentary small cell lymphoma (29), acute gastroenteritis (48), and healthy controls (119). Methods Retrospective study comparing serum electrolyte concentrations at time of diagnosis among the 4 groups of cats, and associations with clinical signs, intestinal mucosal fibrosis scores, treatment subclassification and outcome in CIE. Results Cats with CIE had lower sodium and higher potassium concentrations and lower sodium: potassium ratios compared with healthy cats (P < .001, P = .01, and P < .001, respectively). Cats with CIE and a duodenal mucosal fibrosis score of 2 had lower sodium and lower total calcium concentrations compared with cats that had a score of 0 (P = .02 and P = .01). Cats with CIE and a colonic mucosal fibrosis score of 1 had higher potassium concentrations and lower sodium: potassium ratios compared with cats that had a score of 0 (P = .03 and P = .01). Cats with CIE that died as a result of their disease had higher potassium concentrations and lower sodium: potassium ratios compared to cats that were alive (P = .02 and P = .01). Conclusions and Clinical Importance Electrolyte abnormalities occur with CIE and, in particular, in cats with higher fibrosis scores and worse outcomes. Further research should aim to determine the pathogenesis of these findings and identify novel therapeutic targets for cats with CIE.