Background: Preschool teachers’ well-being is positively associated with their students’ development and learning outcomes. Developing a positive psychological intervention that can foster preschool teachers’ well-being would be essential.Purpose: This study examined the effects of an intervention based on the PERMA (i.e., positive emotion, engagement, relationships, meaning, and accomplishment) model on well-being outcomes among preschool teachers in Hong Kong.Method: We recruited 116 preschool teachers (Mage = 34.14 years, SD = 10.17, range = 21–59; female = 98.51%). Participants were randomly assigned to the intervention (n = 51; received four online workshops that cultivated the PERMA dimensions in 4 weeks) and waitlist control group (n = 65; only received the workshops after the data collection). Participants completed a survey that measured the PERMA dimensions of well-being at baseline 4- and 8-week follow-up occasions. MANCOVA and ANCOVA, controlling for gender, age, and teaching experience, were employed to examine the intervention effects.Results: A significant time x group interaction effect was found in the MANCOVA, Wilks’ Lambda F(10,102) = 2.19, p = .02, η2 = .18. The results of ANCOVA revealed that participants in the intervention group scored significantly higher on engagement, relationship, and accomplishment (η2 = .02 to .05, p < .05) than those in the control condition across time.Conclusion(s): Our findings highlighted the effects of PERMA-based interventions to promote mental health of preschool teachers. Teachers are encouraged to engage in positive psychological activities (e.g., positive reappraisal and self-compassion) to cultivate their well-being. Copyright © 2023 ICBM.