If our chosen aim in science education is to be inclusive and to improve students' learning achievements, then we must identify teaching methodologies that are appropriate for teaching and learning specific knowledge. Karagiorgi and Symeo (2005) remind us that instructional designers are thus challenged to translate the philosophy of constructivism into current practice. Thus, research in science education must focus on evaluating intervention programs which ensure the effective construction of knowledge and development of competencies. The present study reports the elaboration, application and evaluation of a problem-based learning (PBL) program with the aim of examining its effectiveness with students learning Environmental Education. Prior research on both PBL and Environmental Education (EE) was conducted within the context of science education so as to elaborate and construct the intervention program. Findings from these studies indicated both the PBL methodology and EE as helpful for teachers and students. PBL methodology has been adopted in this study since it is logically incorporated in a constructivism philosophy application (Hendry et al. 1999) and it was expected that this approach would assist students towards achieving a specific set of competencies (Engel 1997). On the other hand, EE has evolved at a rapid pace within many countries in the new millennium (Hart 2007), unlike any other educational area. However, many authors still appear to believe that schools are failing to prepare students adequately in EE (Walsche 2008; Winter 2007). The following section describes the research that was conducted in both areas so as to devise the intervention program.