Patients with Parkinson's disease must face changes in their physical, mental, and social functions. One such critical changes is that in the psychological dimension; psychological changes that can produce fatigue and depression. This study explored depression and its associated factors in patients with Parkinson's disease. In this cross-sectional correlational study, 130 participants were recruited for interview. Four inventories, namely the geriatric depression scale, fatigue inventory, social support, and basic demographic data, were completed. Data were analyzed using independent t tests, analyses of variance, the Pearson product-moment correlation coefficient, and linear multiple regression. The multiple regression analysis results revealed that marital status, Hoehn and Yahr stage, number of comorbidities, social support, and degree of fatigue could explain 28.3% of depression variance and were related to depression severity. Marital status had a significant influence on depression. Patients without spouses had higher depression scores than did married patients. The factors of having a spouse, a lower Hoehn and Yahr stage, fewer comorbidities, more social support, and a lower degree of fatigue were all correlated with a lower degree of depression. Nurses should note that patients with Parkinson's disease may experience depression and subsequent fatigue in different stages of disease progression. The rigorous provision of advice to patients with Parkinson's disease is necessary. Nurses should encourage patients to attend hospital and community activities, improve their social lives, and reduce their loneliness to enable their depression and subsequent fatigue to be reduced to the lowest possible degree.