This study investigated the effects of leisure and social activities on the ability of middle-aged adults to maintain activities of daily living (ADL), and whether performing these activities alone or with others contributed to the ability to perform ADL. The study used nationally representative longitudinal data of 22,770 adults in Japan, aged 50-59 years, who did not have limitations in performing ADL at the beginning of the 5-year survey period. The study considered six activity categories: two leisure activities ("hobbies or cultural activities" and "exercise or sports") and four social activities ("community events," "support for children," "support for elderly individuals," and "other social activities"). Multiple logistic regression analysis was used to examine the relation between participation in these categories at baseline and difficulties in ADL at the 5-year follow-up. The association between the extent of social interaction during these activities ("by oneself," "with others," or "both") and difficulties in ADL was also investigated. The analysis yielded significant negative correlations between "exercise or sports" and difficulties in ADL for both men and women, and between "hobbies or cultural activities" and difficulties in ADL for women. However, these significant relationships occurred only when activities were conducted "with others." The present findings might help prevent deterioration in middle-aged adults' performance of ADL in Japan.