Obesity is one of the most frequent nutritional problems in dogs. Obese dogs have a decreased life span and multiple metabolic disorders. The aim of this study was to evaluate the comorbidities in obese dogs admitted at School of Veterinary Medicine and Animal Science, Unesp/Botucatu, São Paulo state, Brazil. Thirty-eight obese dogs were evaluated. Obesity was diagnosed based on body inspection and direct palpation. Dogs were classified according to their body condition score (BCS) using a 9-point system, in which animals that presented scores of 8 and above were considered obese. Medical conditions observed were classified into: respiratory, gastrointestinal, cardiac, urinary, endocrine, dermatologic, neurologic and ophthalmologic changes, locomotor disorders and neoplasms. Of the 38 dogs, 18.4% had no pathology. Twenty eight dogs (73.7%) had an underlying disease, 5.3% with diseases in two different systems and a one dog (2.6%) had concomitant disorder in three different systems. The locomotor system was most affected in 21% of the obese dogs. Neoplasms occurred in 15.8%, followed by dermatological and respiratory alterations, with 10.5% each. Comorbidities in locomotor system included hip dysplasia, arthritis, patellar luxation, intervertebral disc disease and elbow dysplasia. Neoplasms included lipoma, melanoma, squamous cell carcinoma, hemangioma and lung metastasis. In conclusion, obese dogs have several comorbidities, predominantly locomotor changes and neoplasms. Knowledge of these characteristics can assist the clinician in the recognition and management of risk factors and diseases associated with obesity in dogs.