ABSTRACT Objective To evaluate the long-term safety and effectiveness of ipragliflozin in real-world clinical practice in Japanese patients with type 2 diabetes mellitus (T2DM). Research design and methods This post-marketing surveillance study (STELLA-LONG TERM) included Japanese patients newly initiated on ipragliflozin between 17 July 2014 and 16 October 2015 (data lock: 30 September 2019). Survey items included demographics, treatments, adverse drug reactions (ADRs), vital signs, and laboratory variables. Results Of 11,424 registered patients, safety and efficacy analysis sets comprised of 11,051 and 8,763 patients, respectively. ADRs occurred in 2,129 patients (19.27%) and serious ADRs occurred in 210 patients (1.90%). Renal and urinary disorders (n = 739, 6.69%), particularly polyuria/pollakiuria (n = 612, 5.54%) and volume depletion-events, including dehydration (n = 243, 2.20%), comprised the most common ADRs. Mean (SD) change in hemoglobin A1c (─0.66 [1.25] %), fasting plasma glucose (─28.8 [50.1] mg/dL) and body weight (─3.33 [4.32] kg) from baseline to 36 months were statistically significant (P < 0.001). Conclusions The safety profile of long-term ipragliflozin treatment in routine clinical practice is consistent with previously reported interim data at 12 or 24 months and pre-approval clinical trials. Ipragliflozin treatment was also associated with sustained improvements in efficacy parameters for over 3 years.