Suicide is a major public health issue worldwide, and telephone counseling is an important preventive measure. As the number of telephone counselors is insufficient in Japan, public needs cannot be fully met. Willingness is important for securing telephone counselors, but few studies have examined the willingness to engage in telephone counseling activities. Therefore, we investigated the relationship between telephone counselors’ willingness to perform their activities and their psychological characteristics, health status, and received social support. In this study, a questionnaire survey was conducted by mail among telephone counselors belonging to the Federation of Inochi No Denwa in Japan. The total number of valid responses was 709 (recovery rate: 50.4%). Following an exploratory factor analysis, three factors were extracted: (1) willingness to engage in telephone counseling activities, (2) sense of being burdened by telephone counseling activities, and (3) sense of difficulty in coping. Structural equation modeling, using all the factors, showed that social support and grit were directly related to the willingness to engage in telephone counseling activities, while physical health, mental health, and general self-efficacy were indirectly related to it. The findings obtained may be useful in devising concrete measures for telephone counselors to continue their activities.