This study examined depressive symptoms, sleep disturbance, and quality of life in 35 patients with Parkinson's disease. Results showed that nocturnal sleep disturbance, depressive symptoms, and motor disease severity accounted for over two-thirds of the variance in quality of life scores. Depression was the largest predictor of quality of life, uniquely explaining 21% of the variance. Nocturnal sleep disturbance was associated with depressive symptoms as well as with daytime sleepiness. Overall, these data highlight the need to screen patients for even mild levels of depression because its relationship with sleep and quality of life are evident early in the disease course.