Despite the increasing popularity of offline "meetups" among online community participants, little is known about their effect on the health and function of these communities. Using longitudinal network data of both public and private communications among participants of an online community for science fiction fans, this study represents one of the first systematic assessments of the impact of meetups on community participation and members’ bridging and bonding social capital. Results showed that meetups would enhance attendees’ bonding social capital, but that increase would come at the expense of bridging social capital, reducing the opportunity for new members to join and find acceptance in the community. The effect of meetup on community participation was mixed.