Many seniors live in old residential communities (ORCs) with low-quality outdoor environment (OE), which hinders the residents’ outdoor daily activities (ODAs). This paper empirically investigates the association of OE on ODAs for seniors living in ORCs. A questionnaire was designed and distributed in six central districts of Nanjing city. A total of 258 questionnaires was finally collected, of which 60.08%, 29.46%, 9.69%, and 0.78% respondents were scattered into four age groups (61–69, 70–79, 80–89, and ≥90), respectively. Based on reliability analysis, correlation analysis, and regression analysis, the results show that: (1) social activities are mainly associated with noise; (2) leisure activities are significantly associated with road accessibility, slip-resistance measures, greenery, and staff; (3) utilitarian-type activities are significantly associated with stairway accessibility, slip-resistance measures, greenery, and seating; (4) there is a significant association between nature-exposure activities and layout, greenery, and poor air quality. The findings could guide Chinese officials when renewing ORCs by addressing the most important outdoor environmental factors associated with ODAs.