This article aims to document the findings of a professional development intervention study seeking to promote in-service preschool teachers' professional growth about education for sustainability (EfS) through media literacy (ML). The overall aim of this year-long action research project (based on the Analyze, Design, Develop, Implement and Evaluate or ADDIE approach) was to foster teachers' knowledge and awareness regarding EfS via a professional development program incorporating media literacy education. Four preschool teachers participated in the professional development program. Participants' in-class EfS implementations before and after the professional development program were examined utilizing interview, stimulated recall interviews, field notes and content analysis of teacher daily and monthly plans. The principal outcome of the study was that the proposed professional development program does, indeed, lead to the growth of the early childhood teachers' EfS knowledge and awareness. In the short term, examination of participants' pre/post intervention teaching activities indicated that fostering teachers' ML skills helped when designing EfS activities since they were able to access, analyze & evaluate and create EfS related media resources more effectively. Longer-term, the teachers involved in the study incorporated an increased number of EfS related activities in-class, as evidenced by their post-intervention daily and monthly plans.