After the Fukushima Daiichi Nuclear Power Plant accident in March 2011, residents perceived a radiation exposure risk. To address the concerns about radiation exposure and the subsequent effects on their health, we developed the gatekeeper training program for radiation health anxiety and mental health issues. The program consisted of a presentation and roleplay, with educational objectives to the increase knowledge and understanding around radiation health anxiety, alcoholism, depression, and suicide. Twenty-six counselors participated in the program as a single-arm intervention. To measure the outcomes, the subjects reported self-confidence when they counselled with residents with radiation health anxiety and other mental health issues. Comparing the answers to pre-and 2-month follow-up surveys, the confidence levels were higher after 2 months than at baseline, especially for the question “How confident are you at supporting a resident with mental health issues?”, which showed the largest increase (p < 0.001). Regarding radiation health anxiety the questions “Can you communicate coping skills to a resident with radiation health anxiety?” (p = 0.007) and “Can you refer a resident with radiation health anxiety to professionals who can cope appropriately?” (p = 0.016) showed significant increases in their confidence levels. This program could be useful for on-going health activities and future nuclear disasters.