In the present study, we examined the current situation of nurses with mental illnesses, the stigma associated with these illnesses, and nurses' and nurse managers' perceptions of workplace mental health issues. We conducted a questionnaire survey of 880 nurses and nurse managers in Japan. After we carried out a descriptive analysis to examine the characteristics of stigma, the data of 585 participants were used for comprehensive analyses. In all, 71% of participants reported having worked with nurses with mental illnesses, and 40% reported having supported them. Of the participants, 90% believed a growing number of nurses would have mental illnesses in the near future. Stigma scores were significantly higher for items related to nurses with mental illnesses than for those with physical health problems. There was no significant difference in stigma scores according to sociodemographic and organizational characteristics. Scores for stigma items related to nurses with mental illnesses were significantly higher for participants who had worked with or supported nurses with such illnesses than for those who had not. Our findings suggest that effective approaches are needed to decrease stigma, ensure support in the workplace, and address mental illnesses to counter nurse absenteeism.