Team teaching as a close form of teacher collaboration entails frequent interactions between the team-teaching partners in the classroom. During these interactions, the team teachers experience a variety of positive and negative emotions, triggered by their team partner. The teachers may express or suppress these emotions, depending on their habitual use of these emotion regulation strategies. In turn, the teachers' daily emotions may be related to an important facet of teacher well-being, namely their daily work engagement. This study aims to investigate the related factors (habitual emotion regulation, daily work engagement) of team teachers' daily positive and negative emotions triggered by the team partner in the classroom. Forty-seven Austrian team teachers working in secondary education completed a daily diary study, consisting of 15 diary entries, measuring their habitual emotion expression and suppression strategies, their daily positive and negative affect and daily work engagement. Multilevel regression analyses were conducted. Results show that positive and negative affect and work engagement vary substantially within and between team teachers. Random-intercept fixed-slope multilevel models indicate that the habitual use of authentic display of positive emotions is associated with daily positive affect, and teachers' daily positive and negative affect significantly relate to their daily work engagement both on the within- and between-person level. This study underscores the important role that team teachers' emotional experiences play regarding their work engagement. We draw theoretical and practical implications for the role of emotions during team-teaching practices.