Introduction: Literature indicates that nurses__ampersandsignrsquo; job performance in the health care system in Nigeria is deteriorating. Objective: To investigate the relationship between occupational stress and job performance among nurses in a tertiary institution in Nigeria. Methods: Descriptive (survey) design was adopted for the investigation. A purposive sampling technique was used to select two hundred and twenty-two (222) nurses from a population of 500. A reliable and valid occupational stress questionnaire constructed by the researchers was used in data collection. Questions were answered using simple percentages. Results: The results indicated that nurses experience occupational stress (91.0%); Identified stressors were workload (67.1%), inadequate motivation (64.9%), role conflict/ambiguity (54.5%) and poor working conditions (53.6%). Furthermore, it was revealed that occupational stress affected nurses__ampersandsignrsquo; performance of some of their caring duties. Conclusion: Nurses __ampersandsignlsquo;job performance was influenced by the identified stressors. Government should train more nurses, deploy them to clinical settings to reduce workload; staff should be adequately motivated, roles and responsibilities be clearly defined and working conditions made conducive at all times.