The present study addresses the concern for the well-being of teachers and school personnel by examining the efficacy of a multicomponent positive psychology intervention aimed at enhancing emotional well-being in the school environment. The study design comprised a clustered randomized controlled trial, targeting teachers and school personnel working in Finnish basic education. Data collection encompassed the utilization of both the Experience Sampling Method (ESM, n = 241) to assess state-like emotions and questionnaires (n = 245) to evaluate trait-like emotions. The results showed a post-intervention increase in state-like distinct emotions of interest and a trend towards increased engagement in the intervention group, and conversely, increased stress in the control group. Positive trait-like emotions increased in the intervention group post intervention. The intervention further resulted in decreased stress and loneliness amongst teachers and school personnel when in the company of students, and decreased stress while working. The results indicate that positive psychology interventions may be efficacious in enhancing teachers' emotional well-being. Additionally, assessing both state- and trait-like emotions contributes to a broader understanding of this efficacy, whilst measuring teachers' experienced emotions can increase ecological validity.