OBJECTIVE: To determine real-world trends in antidiabetic drug use, and persistence and adherence, in Japanese patients with type 2 diabetes mellitus (T2DM). DESIGN: Retrospective evaluation of administrative claims data (2011-2015) using the Japan Medical Data Center (JMDC) and Medical Data Vision (MDV) databases. SETTING: Analysis of two administrative claims databases for Japanese patients with T2DM. PARTICIPANTS: Adults (aged >/=18 years) with an International Classification of Diseases, 10th Revision code of T2DM and at least one antidiabetic drug prescription. MAIN OUTCOME MEASURES: Treatment patterns in untreated (UT) or previously treated (PT) patients receiving antidiabetic therapy; persistence with treatment at 12 months; adherence to treatment at 12 months. RESULTS: 40 908 and 90 421 patients were included from the JMDC and MDV databases, respectively. The most frequently prescribed therapy at the index (first prescription) date was dipeptidyl peptidase-4 inhibitor (DPP-4i) in UT patients (JMDC: 44.0%, MDV: 54.8%) and combination therapy in PT patients (74.6%, 81.1%). Most common combinations were DPP-4i plus: biguanide (BG; 11.4%, 10.9%), sulfonylurea (SU; 8.4%, 11.0%) or BG+SU (7.8%, 9.1%). In UT or PT patients from either database whose index prescription was for any antidiabetic drug class(es) other than DPP-4i, the most frequent add-on or switch was to DPP-4i. 12-month persistence with index monotherapy was highest with DPP-4i and BG. Adherence was high (>/=80%) for all monotherapy schedules, except insulin and glucagon-like peptide-1 agonist, and for the five most frequent two-drug and three-drug combinations. Persistence was greater in elderly UT patients and in those receiving =5 medications, but comparatively worse in UT patients with >/=3 index antidiabetic drug classes. CONCLUSIONS: The findings indicate that DPP-4i is the most commonly used antidiabetic drug class in Japanese patients with T2DM, and persistence and adherence to this antidiabetic drug class are high.