The growing concerns regarding the risks of transmitting the COVID-19 virus have intensified the job-related stressors commonly encountered by teachers in various cultural contexts. Evidence shows how the COVID-19 crisis has negatively impacted teachers' mental health outcomes such as stress, depression, and quality of life, which highlights the significance of designing psychological programs to boost teachers' well-being. This study examined the effects of a well-being intervention based on the Positivity, Relationship, Outcomes, Strength, Purpose, Engagement, and Resilience (PROSPER) framework on well-being outcomes among 76 in-service teachers (Mage = 26.05 years, SD = 4.71, range = 20–45; female = 93.4%) in Hong Kong. Participants completed survey measures associated with the seven PROSPER outcomes at baseline and 2-month follow-up. Multivariate regression analysis indicated that there were statistically significant multivariate effects for intervention conditions, Wilks' Lambda F(7, 58) = 4.50, p =.01. Results demonstrated that teachers who were assigned to the intervention condition (n = 36) had significantly higher scores than those in the control condition (n = 40) on positivity (b = 0.41, 95% CI [0.16, 0.65], p =.01), strength (b = 0.62, 95% CI [0.23, 1.01], p =.01), purpose (b = 0.61, 95% CI [0.18, 1.04], p =.01), and resilience (b = 0.57, 95% CI [0.07, 1.07], p =.04). Our findings provide evidence on the mental health benefits of the PROSPER-based psychological intervention program for preschool teachers. Copyright © 2022 Society for the Study of School Psychology. Published by Elsevier Ltd. All rights reserved.