In this study, the impact of training supported by the TUBITAK 2237-A Grant Program for Scientific Training on the self-efficacy of pre-service science teachers (PSSTs) in implementing the constructivist approach and delivering distance education (DE) was investigated. The research employed a single-group pretest-posttest experimental design, a quantitative research design. The study's population comprised PSSTs enrolled in science teaching programs across 27 universities in Turkiye, with a sample of 32 preservice teachers selected through criterion sampling. Data were collected using the distance education competence scale and self-efficacy scales for applying the constructivist approach. The analysis involved both descriptive and statistical methods. The results revealed a significant enhancement in the self-efficacy of PSSTs in both distance education delivery and the application of the constructivist approach through the online education. This improvement was attributed to the direct experiences and mentor support gained during the training program, as discussed in the study.