This study explores the effect of an innovative course examining Greek elementary student teachers' (STs') efficacy beliefs and self-confidence for curriculum-based teaching on "Studies for the Environment" topics. These two variables are influencing teachers' ability to teach environmental issues for young children. Five new factors were also examined for their influence on STs' self-efficacy and self-confidence: the role of workshops and simulations, teacher-student interchange role, teaching observation, analysis of other teachings and student-assessed teaching. The study provides useful guidelines for teacher preparation programmes towards the implementation of textbook-free and curriculum-based teaching that maximise students' learning. A pre/post/6 month-delay-post research design using both quantitative (STEBI and factors' ranking) and qualitative (interviews) research tools were implemented in two cohorts of pre-service teachers (N[subscript 1] = 25, N[subscript 2] = 16). Quantitative data were subjected to significance testing and effect sizes analysis, and triangulated with bottom-up categories developed from interviews. Results indicate a considerable and durable increase in STs' personal and outcome expectancy self-efficacy beliefs scores. In respect of the STs' self-confidence, pedagogical content knowledge and especially its sub-factors of Studies for the Environment Pedagogy, reflection, and teaching experience were the most influential factors, while some inertia in the increase of self-confidence was also observed.