Objective: Stress assessments are due to be conducted in December 2015. It is expected that there will be an increase in the number of private health agencies that provide stress assessment services and mental health care. This study aimed to clarify the current situation of and the factors related to stress assessments conducted by nurses in occupational health agencies. Methods: Nurses working full time were randomly selected from 60 organizations that were members of the National Federation of Industrial Health Organization. Self-administered questionnaires were sent out between November 2013 and January 2014. The questionnaire included the personal attributes of the participants, training programs, job contents, and how practical mental health care, including stress assessment, is. The study was approved by the ethics committees in the respective organizations. Results: Out of the 162 questionnaires that were distributed, 89 (54.9%) were returned and 85 (53.1%) were valid for analysis. Stress assessments were conducted by 38.8% of the participants. With reference to their confidence in conducting stress assessments, "confidence and" 70.6%, respectively. The groups that conducted and did not conduct the stress assessments did not show any differences in the findings or other attributes. Further, the implementation of stress assessment was not associated with occupational health nurse (OHN) training, education, position, age, years of experience, attendance of lectures on mental health, etc. However, the confidence in conducting the assessment was related to age when dealing with cases on confidence stress assessment consultation in follow-up to the implementation of screening, such as stress, persons at high risk, and so on. Conclusion: Approximately 40% of the nurses were already conducting stress assessments, but most of them conducted such assessments about once a year and were not deeply involved in them. Approximately 70% of the nurses were confident in implementing stress assessments. Further, they reported that they were confident to do so even if OHNs were not involved. We found that to encourage OHNs in occupational health agencies to provide mental health care and stress assessments, practical training programs are required. Such programs should include a series of stress assessments and help foster cooperation with superiors, colleagues, and occupational health staff such that the OHNs obtain experience and confidence.