The purpose of this study is to investigate the effects of the Project-Based Learning (PBL) method on undergraduate students' achievement and its association with these students' self-efficacy beliefs about science teaching and pinions about PBL. The sample of the study consisted of two randomly chosen classes from a set of seven classes enrolled in the Science Teaching Course in a Primary School Education Department of a State University in Turkey. The randomly assigned treatment group (n =33) was instructed based on a PBL method. The control group (n = 33) was instructed through the use of a traditional teaching (TT) method. The Science and Technology Teaching Achievement Test (STTAT) and self-efficacy belief scale (SEBS) were used as pre- and post-test measures. The results showed that students in the treatment group produced better performance on the Post- SEBS and the Post-STTAT. The students in the treatment group expressed mostly positive opinions about the use of the Project-Based Learning method.