The purpose of this study was to examine the effects of stress on the job performance of psychiatric nurses in the Ankaful Psychiatric Hospital in Cape Coast. A descriptive survey design was adopted for the study. A sample of 150 psychiatric nurses were selected from a population of 197 psychiatric nurses using a simple random sampling procedure. Data were collected using the Weiman Occupational Stress Scale (WOSS) questionnaire. 143 answered questionnaires were retrieved out of the 150 questionnaires offered, giving a 95% return rate. Data were analysed using both descriptive and inferential statistics. The study revealed that the psychiatric nurses' job performance were negatively affected due to the effects of stress, which include mild to severe headache, loss of concentration, exhaustion, anger, overreaction, finding excuses and absence from work, and forgetfulness. The study recommended that the hospital authorities structure the work schedules of psychiatric nurses so that the nurses can get intermittent periods of leave away from work while providing the logistics to make the work of psychiatric nurses easy.