Objective <p>This study was conducted in order to evaluate the effect of insulin administration training provided to patients with Type 2 diabetes mellitus who use insulin on their safe medication usage, pain levels, and treatment perception.</p> Methodology <p>A randomized controlled trial was designed. This study was conducted with a total of 84 patients (43 in the experimental group and 41 in the control group) diagnosed with Type 2 diabetes who were admitted to a public hospital in the Southeastern Anatolia Region of Turkey between October 2022 and March 2023. The patient information form, Insulin Administration Skill Observation Form, Visual Analog Scale, and Insulin Treatment Appraisal Scale were used. The experimental group was provided with individualized training and a booklet on the use of insulin.</p> Results <p>Both posttest and retention test measurements were taken after the insulin administration training. According to these measurements, insulin administration skill and insulin treatment perceptions of the experimental group were significantly higher than those of the control group, while their pain intensity score was significantly lower (<i>p</i> &lt; 0.001).</p> Conclusion <p>The results of this study revealed that the insulin administration training increased safe medication application and insulin treatment perceptions of the patients in the experimental group and lowered their pain levels.</p> Trial registration <p>ClinicalTrials.gov = NCT05915338.</p>