Background <p>Electronic cigarette (E-cig) use is rising among youth; however, formal vaping education remains limited within undergraduate medical curricula. As a result, medical students may enter practice with misconceptions and limited counselling confidence. This study evaluated the educational impact of a brief animated intervention on Thai medical students’ knowledge and confidence in communicating E-cig health risks.</p> Methods <p>A prospective cohort study with repeated measures without a comparison group was conducted among 157 medical students (Years 1–6) at a Thai medical school. A seven-minute animated video developed by medical students addressed five domains: risks and safety, chemical composition, side effects, health consequences including EVALI, and misconceptions regarding smoking cessation. Participants completed online questionnaires at pre-intervention, immediate post-intervention, and three-month follow-up. Outcomes included knowledge scores and self-reported counselling confidence.</p> Results <p>Of 157 students, 56% were female and the median age was 20.5 years. Among the 57 participants who completed assessments at all three time points, mean knowledge scores increased from 18.4 ± 3.58 at pre-intervention to 26.08 ± 3.12 immediately post-intervention, and remained higher than baseline at three-month follow-up (22.36 ± 5.09) (<i>P</i> &lt; 0.001). Improvements were most pronounced in domains related to chemical composition, side effects, and EVALI. Counselling confidence also increased from 4.8 ± 2.2 to 7.5 ± 1.7 and remained elevated at follow-up (7.2 ± 1.4; <i>p</i> &lt; 0.001).</p> Conclusions <p>A brief student-developed animated intervention was associated with improved knowledge and counselling confidence among medical students with minimal prior vaping education. Concise digital learning tools may support integration of emerging public health competencies into undergraduate medical curricula.</p>