Background: Sodium-glucose cotransporter-2 (SGLT2) inhibitors are effective treatments for type 2 diabetes mellitus (T2DM). We present the interim findings of an ongoing post-marketing surveillance (PMS) study in Japanese patients with T2DM receiving empagliflozin. Research design and methods: This 3-year, prospective, observational, multicenter PMS evaluated the safety and effectiveness of empagliflozin in Japanese clinical practice. Patients with T2DM who had not been treated with empagliflozin before enrollment were eligible. Assessments, including the primary endpoint of incidence of adverse drug reactions (ADRs), were based on electronic case report forms (eCRF). Results: Of 8,180 registered patients from 1,103 sites, 7,618 patients had an eCRF including a follow-up visit and were treated (mean age, 58.8 years; 10.5% aged ≥75 years; 63.2% male; mean HbA1c, 8.01%; 41.8% with HbA1c ≥8.0%; 24.8% and 61.8% with at least mild hepatic and renal impairment, respectively). Mean treatment duration was 98.4 weeks; 644 (8.5%) patients had ≥1 ADR, including 8.5% of patients aged ≥75 years. Hypoglycemia, urinary tract infection, genital infections, volume depletion, diabetic ketoacidosis, and lower limb amputation occurred in 0.28%, 0.62%, 0.53%, 0.33%, 0%, and 0.03% of patients, respectively. Conclusions: The reported ADRs were consistent with the known safety profile of empagliflozin. Trial registration: ClinicalTrials.gov identifier: NCT02489942.