Older adults (aged 65+) are still less likely to adopt the Internet when compared to other age groups, although their usage is increasing. To explore the societal effects of Internet usage, scholars have been using social capital as an analytical tool. Social capital pertains to the resources that are potentially available in one's social ties. As the Internet becomes a prominent source of information, communication, and participation in industrialized countries, it is critical to study how it affects social resources from an age-comparative perspective. Research has found a positive association between Internet use and social capital, though limited attention has been paid to older adults. Studies have also found a positive association between social capital and wellbeing, health, sociability, and social support amongst older adults. However, little is known about how Internet usage or lack thereof relates to their social capital. To address this gap, we used a mixed-methods approach to examine the relationship between Internet usage and social capital and whether and how it differs by age. For this, we surveyed a representative sample of 417 adults (18+) living in Lisbon, Portugal, of which 118 are older adults. Social capital was measured through bonding, bridging, and specific resources, and analyzed with Latent Class Modeling and logistic regressions. Internet usage was measured through frequency and type of use. Fourteen follow-up semi-structured interviews helped contextualize the survey data. Our findings show that social capital decreased with age but varied for each type of Internet user. Older adults were less likely to have a high level of social capital; yet within this age group, frequent Internet users had higher levels than other users and non-users. On the one hand, the Internet seems to help maintain, accrue, and even mobilize social capital. On the other hand, it also seems to reinforce social inequality and accumulated advantage (known as the Matthew effect).