Background: The current cross-sectional study examines a model that was designed to advance understanding of the interplay between compassion towards teachers expressed by teaching colleagues, subjective happiness, proactive strategies and kindergarten teachers’ levels of work engagement, and perceived working environment fit. Methods: The research was conducted with a sample of 319 full-time in-service kindergarten teachers at Italian public preschools—a context in which a few previous studies have been carried out. Self-report questionnaires were administered: The Subjective Happiness Scale, the Santa Clara Brief Compassion Scale, the Utrecht Work Engagement Scale, the Proactive Strategy Scale, and the Teacher-working environment fit scale. Data were analyzed by using the structural equation modelling (SEM) approach. Results: Results show that compassion and subjective happiness have a direct positive total effect on work engagement, whereas the effects of compassion and subjective happiness on experienced working environment fit suggest that the association among constructs is mediated by the role of proactive strategies. Conclusions: Based on these findings, we strongly advocate that educational policy makers and head teachers’ pay close attention to the areas of personal and collective resources and work-related well-being, with a view to effectively address the promotion of early childhood teachers’ work engagement and working environment fit.