A 9-month-old, female Labrador retriever mix was presented for two types of seizure-like episodes, one of which occurred only during sleep. The two types of episodes were morphologically distinct. An electroencephalogram (EEG) demonstrated that the sleep-associated episodes occurred during rapid eye movement (REM) sleep, supporting a diagnosis of a REM behavior disorder. Based on their morphology and response to antiseizure medications, the waking episodes were diagnosed as seizures. The animal was also diagnosed with an obsessive-compulsive and generalized anxiety disorder. The REM behavior disorder and anxiety-related behaviors improved with tricyclic antidepressant therapy.