Background <p>Cognitive decline poses a major public health challenge, while individual trajectories are heterogeneous and modifiable. Social engagement is a potential influnencing factors, but the long-term cognitive implications of sustained engagement in distinct modes remain unclear.To address this gap, this study investigates the association between longitudinal patterns of social interaction and domain-specific cognitive trajectories in older adults.</p> Methods <p>This study analyzed 9-year data (2012–2021) from the English Longitudinal Study of Ageing (ELSA). Cognitive function was assessed across three domains: orientation (<i>n</i> = 2394), execution (<i>n</i> = 2113), and memory (immediate memory and delayed memory) (<i>n</i> = 2415). Participants were classified into four groups based on their longitudinal social engagement patterns: continuous online/no social interaction group, continuous face-to-face group, continuous mixed group, changes group. Growth mixture modeling identified cognitive trajectories, and multinomial logistic regression examined their association with social patterns.</p> Results <p>Three distinct trajectories were identified in each cognitive domain. For orientation and executive function, compared to the “continuous online/no social interaction” group, membership in the “continuous face-to-face”, “continuous mixed”, or “changes” groups were significantly more likely to remain at a stable and high level (all ORs &lt; 1,<i> P</i> &lt; 0.05). No significant associations were found between social interaction patterns and memory trajectories (immediate memory and delayed memory).</p> Conclusions <p>Face-to-face social interaction was associated with greater stability and less decline in orientation and executive function among older adults. These findings underscore the importance of in-person social interaction for maintaining cognitive health and support personalized, pattern-specific recommendations for cognitive health promotion.</p>