Background <p>Cognitive impairment is a major public health challenge globally. While pain is a known risk factor for cognitive decline, its dyadic effects within couples remain poorly understood. This study aimed to investigate the actor and partner effects of pain on cognitive function among middle-aged and older Chinese couples, and to examine the mediating roles of depression and social participation.</p> Methods <p>This cross-sectional study used data from the 2020 China Health and Retirement Longitudinal Study (CHARLS). A total of 3,046 couples (6,092 individuals) aged 45 years or older were included. The Actor-Partner Interdependence Model (APIM) was used to estimate the association between pain and cognitive function in married couples. The mediating role of depression and social participation was analyzed using the Actor-Partner Interdependence Mediation Model (APIMeM).</p> Results <p>Husbands reported better cognitive function and lower levels of depression than their wives. A higher proportion of wives reported experiencing frequent pain. Pain was negatively associated with cognitive function in both partners. APIM analyzes revealed significant actor and partner effects: an individual’s pain was associated with their own poorer cognitive function (actor effect: <i>β</i> = -0.165 for husbands, -0.207 for wives) and their spouse’s poorer cognitive function (partner effect: <i>β</i> = -0.107 for husbands, -0.154 for wives). Depression fully mediated these associations. In contrast, social participation did not show a significant mediating effect.</p> Conclusions <p>Pain shows interdependent associations with cognitive function within couples, primarily through the pathway of depression rather than reduced social participation. These findings highlight the need for couple-oriented interventions that focus on pain management and mental health to mitigate cognitive decline in aging populations.</p>