Online social network sites provide possibilities to enhance social relationships and engage in cognitive activities for older adults. The present study aimed to investigate the relationship between the use of one social network site, Facebook, and cognitive functions in older adults considering different dimensions of Facebook use together with different cognitive functions. Seventy healthy older adults completed the use of Facebook form, Multidimensional Scale of Perceived Social Support, and Social Network Index. Their cognitive functions were measured with Digit Span Tasks, Free and Cued Selective Reminding Test, Letter and Category Fluency Tests, Stroop Test, Digit Symbol Substitution Test, and Trail Making Test (TMT-A and TMT-B). After controlling for age, gender, education level, we found that Facebook users performed better on TMT-A compared to non-users. Among Facebook users, the length of having an account, the network size, the daily duration of use, and the frequency of active and passive use correlated with cognitive performance after controlling offline sociality. These findings, which need confirmation by experimental and longitudinal studies, suggested that being connected to a larger network via more prolonged and active use of social media might be associated with higher cognitive functioning.