The purpose of this study was to investigate the relationship between the neighborhood built environment (NBE) aspects of age-friendly cities and communities (AFCCs) and social capital in the Korean context. We described and compared age differences when analyzing misfits of AFCC NBE and impacts on social capital. We collected the data (N = 1246) from two Korean communities; our multiple and binary logistic regression outcomes show that AFCC NBE aspects such as outdoor spaces, transportation, and housing are significant predictors of different subcategories of social capital. For the older group, the outdoor spaces misfit was significant for all three subcategories of social capital, but transportation and housing misfits were significant for the social trust and reciprocity index scores. For the middle-aged group, the outdoor spaces misfit was significant for social networking and participation, and a transportation misfit was significant for participation and social trust and reciprocity. Fewer misfits or better fits of outdoor spaces and transportation encouraged more networking, participation, social trust, and reciprocity. Dwelling type was important to predict social capital, especially for the older group. The present study confirmed the importance of AFCC NBE in predicting social capital and unique factors in the Korean context.