Aims To investigate the efficacy and safety of the dipeptidyl peptidase‐4 inhibitor linagliptin in patients with Type 2 diabetes mellitus inadequately controlled by a combination of metformin and pioglitazone. Methods This was a multi‐centre, phase 3, randomized, double‐blind, placebo‐controlled study comparing linagliptin 5 mg once daily (n = 183) and placebo (n = 89) as add‐on to metformin and pioglitazone. The primary endpoint was the change from baseline in glycated haemoglobin (HbA1c) after 24 weeks. Results The placebo‐corrected adjusted mean (se) change in HbA1c from baseline to 24 weeks was –6 (1) mmol/mol –0.57 (0.13)% (P < 0.0001). In patients with baseline HbA1c ≥ 53 mmol/mol (7.0%), 32.4% of patients in the linagliptin group and 13.8% in the placebo group achieved HbA1c < 53 mmol/mol (7.0%) (odds ratio 2.94; P = 0.0033). The placebo‐corrected adjusted mean (se) change from baseline in fasting plasma glucose at week 24 was –0.57 (0.26) mmol/l –10.4 (4.7) mg/dl (P = 0.0280). The incidence of serious adverse events was 2.2% with linagliptin and 3.4% with placebo. Investigator‐defined hypoglycaemia occurred in 5.5% of the linagliptin group and 5.6% of the placebo group. No meaningful changes in mean body weight were noted for either group. Conclusions Linagliptin as add‐on therapy to metformin and pioglitazone produced significant and clinically meaningful improvements in glycaemic control, without an additional risk of hypoglycaemia or weight gain (Clinical Trials Registry No: NCT 00996658). What's new? Combination therapy of two or more oral anti‐hyperglycaemic drugs is often necessary to reach glycaemic targets in patients with Type 2 diabetes mellitus. The combination of metformin and pioglitazone is often prescribed, but, when HbA1c goals are not achieved, treatment guidelines recommend adding a third oral anti‐hyperglycaemic drug. Few studies have evaluated the effects of triple oral therapy with a dipeptidyl peptidase‐4 inhibitor, metformin and pioglitazone. The results of this study show that linagliptin may be an effective and safe treatment option for patients with Type 2 diabetes who have failed to reach glycaemic targets with metformin and pioglitazone.