<p>Background : As of March 2014, three years after the Fukushima nuclear power plant disaster, 58,624 residents were relocated to other regions within the Fukushima prefecture, and 47,683 residents were relocated to other prefectures. Attenuation of human relationships due to the disruption of regional ties nurtured in the past heightens stress. This highlights the need to create a new community focused on establishing ties with neighbors. Among evacuees, providing support for elderly adults suffering from a decline in physical functioning and a deteriorating mental health is necessary. Objective : This study investigated the relationship between individual social capital and mental health in elderly adults, specifically focusing on the role of social capital in reconstruction after the earthquake. Methods : A self-report questionnaire was conducted at Waseda University and Shinsai Shien Network, Saitama. Evacuees from Fukushima prefecture (n=3,599) who lived in Saitama prefecture and Tokyo were asked to complete the Stress Response Scale-18 comprising questions related to social capital with cognitive and structural indicators. There were 772 replies (response rate=21.5%) and 229 respondents were analyzed. In addition, a multiple logistic regression analysis was performed to examine the relationship between social capital and mental health in elderly adults. Results : The group with low confidence in neighbors relative to the group with high confidence in neighbors had a 5.192 times higher chance of being in the high-stress group (95%CI=1.042-25.865). In addition, the group with lower confidence in acquiring their neighbors assistance if a disaster occurred again, had a 2.172 times higher chance of being in the high-stress group (95%CI=1.051-4.487). Furthermore, people who have never participated in regional activities (e.g., hobbies, sports, entertainment, etc.) had a 3.112 times higher chance of being high-stressed relative to the group who participated two or three times (95%CI=1.059-9.150). Finally, the group that never greeted neighbors had a 3.317 times higher chance of being high-stressed relative to the group that had five or more greeted neighbors (95%CI=1.177-9.346). Conclusion : Lower social-capital cognitive indicators such as “trusting one’s neighbors” and “helping one’s neighbors” were correlated with higher stress levels. Therefore, elderly adults can presumably maintain good mental health by developing a neighborhood relationship and building mutual trust. Furthermore, lower social-capital structural indicators such as “number of greeted neighbors” and “participation frequency in regional activities” were correlated with higher stress levels. It is important to encourage social participation of evacuees and provide them with support.</p>