An empirical study was conducted to discern the relationship between adult learners’ online participation, their learning performance, and perceptions of social capital enhancement. Participants (n=171) were adult learners following a blended learning program in Specific Teacher Training at different adult education centers in Flanders (Belgium). A questionnaire was developed to measure adult learners’ socio-demographics, their grade point average (GPA) as measure of learning performance, online participation and social capital enhancement. Multiple regressions were employed to answer the research questions. The findings revealed that adult learners’ online participation was not significantly related to their learning performance. In addition, learners who were older perceived greater enhancement of both bonding and bridging social capital, i.e. age is a significant predictor. As for different types of online participation, not all of them enhanced learners’ perceived social capital. Accordingly, learners who contributed more to discussion reported greater bonding capital (β=.20, ppR²=.17 and R²=.19, respectively. The findings confirm that online interaction should be enhanced to enable greater social capital building among the adult learners whilst findings on the role of online participation with regard to learning have been mixed. In addition, the instructors should pay attention to ensure that learners can assume different roles during online interactions with peers so that both types of social capital can be sustained.