Research knowledge about the role of teachers' personality in shaping their mood is still limited. The present study explores the associations between teachers' five broad personality traits (known as the 'Big Five'), emotion regulation (suppression and reappraisal), and mood. Data collected from a sample of 113 Israeli teachers were analysed using structural equation modelling analysis and cluster analysis. Path model analysis indicated that suppression mediates the relations between teachers' conscientiousness, extraversion, and neuroticism on one hand, and their negative mood on the other, and that reappraisal mediates the relations between teachers' conscientiousness and neuroticism on one hand, and their positive mood on the other. Cluster analysis revealed associations between three personality types of teachers with their emotion regulation and mood. The study clarifies the role that teachers' personality traits play in determining their affective life.