Medical records of 261 cats presenting with gastrointestinal disease that had a serum cobalamin concentration measured were reviewed. In addition, a reference range for cobalamin (305 - 1.967ng/L) was established using 22 healthy adult cats with undetectable levels of urinary methylmalonic acid. A total of 108 of 261 cats (41.4 %) had hypocobalaminemia; 69 cats (26.4 %) had cobalamin concentrations below the detection limit of the assay (< 150ng/L, group A) and 39 (15 %) had concentrations between 150 - 304ng/L (group B). The remaining 153 (58.6 %) cats had normal cobalamin concentrations (group C). Diarrhea was the most common clinical sign in hypocobalaminemic cats and vomiting or anorexia was the most common sign in normocobalaminemic cats. Only cats with both, vomiting and diarrhea were more likely to have hypocobalaminemia than cats with other clinical signs (odds ratio, 2.879; 95 % CI, 1.313 - 6.310). Serum cobalamin concentration was negatively correlated with age of the patient and positively correlated with body condition score. Cats of group A had a significantly higher neutrophil count (p = 0.0009) and higher MCV (p = 0.0064) and significantly lower hematocrit (p = 0.0018) and albumin concentration (p = 0.0037) than cats in other groups. There was no difference between cats of groups B and C with respect to complete blood cell counts and metabolic profiles. Among the diagnoses made in 125 cats (A 69.6 %, B 59 %, C 35.3 %), lymphoma and inflammatory enteropathy were most common. Lymphoma was diagnosed in 31.2 % (A 53.8 %, B 15.4 %, C 30.8 %) and inflammatory enteropathy in 22.4 % (A 35.7 %, B 7.1 %, C 57.2 %) of cats. Hypocobalaminemia is a frequent problem in cats with gastrointestinal disease. Presenting clinical signs as well as laboratory results may already indicate its probability and severity. However, only values below the detection limit of the assay seem to affect routine bloodwork results. Cobalamin should be routinely measured in feline gastrointestinal disease, as its serum concentration may influence the choice of further diagnostics.