Insulin treatment is necessary for many patients with type 2 diabetes, and its delivery must be safe and comfortable. This study evaluated patients’ safety and comfort when using a Gensulin® delivery device, GensuPen (Bioton), a reusable insulin pen device for injecting Gensulin® insulin among adult and elderly patients with type 2 diabetes. This was a 4-week multicenter, prospective, observational, open-label study in patients with diabetes mellitus type 2 who have recently started using a GensuPen. Overall, 10,309 patients (mean age: 63 ± 12.0 years; 47.9% female) were analyzed in this study. Of these, 2.5% had used an insulin delivery device before, and for 97.5%, GensuPen was the first delivery device they had used. Most (87.8%) of the patients rated the GensuPen as very good in setting the dose, 92.0% in confirmation of successful insulin administration, 80.9% in trigger location, and 75.0% in force needed for injection. The overall safety of the GensuPen use was high since severe hypoglycemia occurred only in 0.2% of the studied patients. There were 0.6% adverse events, none of which were serious. This real-life observation data shows that the GensuPen was well accepted and safe in this large patient population of adult and elderly patients with type 2 diabetes.