Affect and cognition have both been associated with communication across one’s social network during ageing. Thus, it is important to consider how communication varies by different aspects of one’s social network, and by communication mode, including phone, email and social media. This study aimed to investigate the relationship between technology-mediated communication, depression and an executive function-related fluid-reasoning measure among older adults. Data were drawn from the Health and Retirement dataset’s 2016 wave. Hierarchical regression analyses were conducted to examine the link between communication modes (phone, email and social media) with children, family and friends with a fluid-reasoning cognition measure and Center for Epidemiologic Studies Depression Scale, controlling for demographic covariates, among 3,798 older American adults. Phone and email communication, but not social media, were significantly related to depression and cognition. The model fit was considerably stronger for the analyses with cognition than depression. Curvilinear associations were found for communication via phone and email with cognition, suggesting moderate amounts of communication by phone and email across social groups were most closely linked with higher scores on fluid reasoning. For depression, curvilinear relationships were found for talking on the phone with family and friends, and emailing for children and family, indicating that moderate communication levels revealed the lowest depression levels. Implications for how older adults’ social support may contribute to depression and cognition status are discussed.