Aim: To investigate acute effects of add-on therapy with the sodium glucose co‐transporter 2 inhibitor tofogliflozin to dipeptidyl peptidase (DPP)-4 inhibitors on 24-hour glucose profile and glycemic variability evaluated by continuous glucose monitoring (CGM) in patients with type 2 diabetes. Patients and methods: We studied 17 patients with type 2 diabetes who were hospitalized for glycemic control. CGM was performed for 7 consecutive days in the last week of hospitalization. Tofogliflozin 20 mg/day was started on day 4 after initiating CGM and was administered to 10 patients receiving DPP-4 inhibitors and 7 patients not receiving DPP-4 inhibitors. We compared several CGM parameters between day 2 to 3 (ie, before treatment with tofogliflozin) and day 5 to 6 (ie, after starting treatment with tofogliflozin). Results: After starting treatment with tofogliflozin, mean 24-hour glucose and postprandial glucose after each meal were significantly decreased in both groups of patients. Time in range (ie, at a glucose level of 70-180 mg/dL) was significantly increased in both groups. The standard deviation of 24-hour glucose and mean amplitude of glycemic excursions, 2 indexes of glycemic variability, were significantly decreased in patients receiving DPP-4 inhibitors but were unchanged in those not receiving these drugs. Conclusions: Add-on therapy with tofogliflozin to DPP-4 inhibitors acutely reduces 24-hour glucose levels and improves glycemic variability in patients with type 2 diabetes.