For effective teamwork, especially in demanding learning situations like a hackathon, coordination is crucial as it contributes to mutual trust and shared mental models of team members. However, teams experience challenges that mar team coordination. Research has shown that interpersonal skills such as socially-shared emotion regulation (SSER) can be key in dealing with such challenges. We examined the relationship between SSER and mutual trust, and SSER and shared mental models in the context of a hackathon. Adapted from a small SSER scale, we built a 27-item questionnaire to examine SSER and its relationship with mutual trust and shared mental models in programming teams. We also used heat maps to provide an overview of individual team members' perceptions of their teams' SSER strategy application, mutual trust, and strength of shared mental model bonds within the team. Regarding the relationship between SSER and shared mental models, our analyses revealed signification association (correlation) between: (1) SSER situation modification and shared mental model: task and communication skills and (2) SSER situation modification and shared mental model: team dynamics and interaction. For the relationship between SSER and mutual trust, our analyses revealed significant relationships between: (1) SSER situation modification and perceived trustworthiness, (2) SSER cognitive change and perceived trustworthiness, (3) SSER response modulation and cooperative behaviors, and (4) SSER response modulation and monitoring behaviors. These relationships highlight the power of SSER in building key team coordination mechanisms and strengthening team performance.