This study explored whether the incorporation of specific research activities into the syllabus could develop the research self-efficacy of a group of English language student teachers in Vietnam who belong to a demographic group currently underrepresented in self-efficacy literature. It also attempted to understand the perceived effects of the intervention on students’ research self-efficacy. The study adopted a quasi-experimental research design and a mixed-methods methodology. Pre- and post-questionnaires along with weekly reflective journal entries were used as data tools. Results indicate that due to their involvement in the intervention, the students in the experimental group displayed a stronger sense of research self-efficacy compared to those in the control group. The students in the experimental group gradually developed their self-efficacy owing to a growth in research knowledge and skills and a therapeutic research-training environment. The findings of the study are informative to the design, refinement, and optimization of future interventions that facilitate the effects of research experiences, knowledge, and skills on undergraduates’ research self-efficacy beliefs.