This study examined how job stress and work support predict the experience of burnout and how burnout is related to absenteeism and job performance in a sample of 73 registered nurses. The current study expanded on previous findings by including supervisor ratings of performance and employee records of absenteeism in addition to self-report measures. It also examined the extent to which burnout may mediate the relationships of job stress and social support with these performance indicators. Analyses indicated that levels of work support and job stress were both significant predictors of burnout. Additionally, higher burnout levels were significantly associated with poorer self-rated and supervisor-rated job performance, more sick leave, and more reported absences for mental health reasons. Finally, further analyses suggest that level of burnout served as a mediator of the relationships between social support and self-rated job performance, absences for mental health reasons, and intentions to quit. The findings suggest that burnout not only may negatively impact healthcare providers, but also may influence objective absenteeism and supervisor perceptions of employee performance.