This study aims to compare the effectiveness of video and paper materials used for teach-back education on the first insulin injection for patients with diabetes. The study enrolled 110 patients hospitalized for diabetes who had received education on their first insulin injection in the endocrinology department. The patients were divided into an intervention group (n = 55) and a control group (n = 55) using convenience sampling. Video materials were employed for the teach-back education of the intervention group, while paper materials were employed for the teach-back education of the control group. We compared cases who answered correctly to the common parts (selection and management of injection devices, selection and rotation of injection sites, proper use of injection angles and pinching, insulin storage, injection-related complications and their prevention, selection of the correct needle length, and safe disposal of needles after use) for the first time, the number of educational sessions and total education duration between the two groups and employed the “My View on Insulin” questionnaire to survey the two groups before and 28 days after the intervention. The intervention group had a shorter total education duration than the control group, a difference that was statistically significant (p < .001). The intervention group had more advantages over the control group in terms of rotation education at the injection site (p < .05). There was no statistically significant difference in the questionnaire scores between the two groups after the intervention (p > .05); however, both groups scored significantly higher than before the intervention, a difference that was statistically significant (p < .001). The teach-back method combined with video materials applied for educating patients on their first insulin injection could reduce the education duration by healthcare providers and improve the patients’ psychological insulin resistance. The key to successfully teaching patients to self-administer insulin, and allowing them to master the steps involved, is to focus on “why” rather than “what” to do.