This study examines the interactional dynamics revealed through teasing humor in the context of a startup business meeting. Using a quasi-conversation analytic approach to details of talk, as well as ethnographic information concerning the community of practice, this study aims to illuminate the construction of professional identities shown in members' participation in teasing humor. The dataset consists of three video-recorded weekly business meetings of a startup (210 minutes) and a supplementary interview and observation notes. The analyses show that, in this business context, the members' identities (e.g., the CEO, the co-founders versus non-co-founders) were revealed in the dynamics of participation in teasing humor. Teasing humor was also found to contribute to finding creative solutions to challenging issues under discussion. The non-co-founders, in particular, found opportunities to participate in the major business discourse through this teasing. By participating in the teasing segments, they were able to present themselves as legitimate members of the startup. The findings are discussed to highlight the sociolinguistic norms of a professional community in creating a constructive business culture.