A significant tension exists between the necessity for teachers to regulate their emotions and the tendency to overlook these emotions in STEM education. Teachers' emotion regulation is inherently context-sensitive and discipline-specific. Therefore, it is crucial for researchers to explore the particularities of teachers' emotion regulation in the context of STEM education. This study presents a scoping review of existing research on STEM teachers' emotion regulation, focusing on theoretical underpinnings, methodological approaches, and research foci. Following scoping review guidelines, a corpus of 23 studies published between 2004 and 2023 was collected and analyzed. Emotional intelligence emerged as the most frequently employed theoretical underpinning for conceptualizing STEM teachers' emotion regulation, followed by emotional labor and emotion regulation. Among the four research approaches--quantitative, qualitative, mixed, and conceptual--the majority of studies adopted quantitative and qualitative methods to investigate the nature and the relational model of teachers' emotion regulation in STEM education. The findings indicate that research on STEM teachers' emotion regulation exhibits imbalances in theoretical and methodological approaches. Although various contexts, antecedents, and outcomes of STEM teachers' emotion regulation have been identified, the scope and depth of these investigations remain limited. Research on STEM teachers' emotion regulation is still in its early stages for several reasons: the paucity of studies in this area, a reliance on broad emotional constructs rather than specific emotion regulation perspectives, and the lack of tailored theoretical frameworks addressing STEM teachers' emotion regulation. This scoping review maps existing knowledge on teachers' emotion regulation in STEM education, elucidates the underlying philosophical standpoints of prior research, and offers recommendations for future research directions.