Background/Objectives: Handgrip strength is a widely used indicator of physical function that is associated with various health outcomes of older adults. However, the relationship between lifestyle factors and handgrip strength, as well as the age-associated relationship between them, remains insufficiently understood. This study examined age-adjusted associations between multiple lifestyle factors and handgrip strength among older women. Methods: During this cross-sectional study of 2,206 older women, handgrip strength was categorized into low, middle, and high tertiles. Lifestyle factors such as dietary status, exercise frequency, sleep quality, social interaction, and outing frequency were assessed using a questionnaire. Group differences were evaluated using an analysis of variance and chi-square tests. An analysis of covariance was performed to examine associations between lifestyle factors and handgrip strength after adjusting for age. Results: Participants in the high handgrip strength tertile were younger and more likely to report favorable lifestyle behaviors. After adjusting for age, dietary status (p = 0.024), social interaction (p = 0.001), and outing frequency (p = 0.017) remained significantly associated with handgrip strength. In contrast, sleep quality (p = 0.073) and exercise frequency (p=0.060) were not significantly associated with handgrip strength after age adjustment. A clear dose–response relationship was observed between lifestyle scores and handgrip strength. Conclusions: Among older women, dietary status, social interaction, and outing frequency were independently associated with handgrip strength, even after accounting for age. These findings suggest that multidimensional lifestyle factors, particularly those related to nutrition and social engagement, may contribute to maintaining physical function in older adults.