Prospective evidence is lacking regarding incremental benefits of long-acting dual- versus mono-bronchodilation in improving symptoms and preventing short-term disease worsening/treatment failure in low exacerbation risk patients with chronic obstructive pulmonary disease (COPD) not receiving inhaled corticosteroids. The 24-week, double-blind, double-dummy, parallel-group Early MAXimisation of bronchodilation for improving COPD stability (EMAX) trial randomised patients at low exacerbation risk not receiving inhaled corticosteroids, to umeclidinium/vilanterol 62.5/25 μg once-daily, umeclidinium 62.5 μg once-daily or salmeterol 50 μg twice-daily. The primary endpoint was trough forced expiratory volume in 1 s (FEV ) at Week 24. The study was also powered for the secondary endpoint of Transition Dyspnoea Index at Week 24. Other efficacy assessments included spirometry, symptoms, heath status and short-term disease worsening measured by the composite endpoint of clinically important deterioration using three definitions. Change from baseline in trough FEV at Week 24 was 66 mL (95% confidence interval CI: 43, 89) and 141 mL (95% CI: 118, 164) greater with umeclidinium/vilanterol versus umeclidinium and salmeterol, respectively (both p < 0.001). Umeclidinium/vilanterol demonstrated consistent improvements in Transition Dyspnoea Index versus both monotherapies at Week 24 (vs umeclidinium: 0.37 95% CI: 0.06, 0.68, p = 0.018; vs salmeterol: 0.45 95% CI: 0.15, 0.76, p = 0.004) and all other symptom measures at all time points. Regardless of the clinically important deterioration definition considered, umeclidinium/vilanterol significantly reduced the risk of a first clinically important deterioration compared with umeclidinium (by 16-25% p < 0.01) and salmeterol (by 26-41% p < 0.001). Safety profiles were similar between treatments. Umeclidinium/vilanterol consistently provides early and sustained improvements in lung function and symptoms and reduces the risk of deterioration/treatment failure versus umeclidinium or salmeterol in symptomatic patients with low exacerbation risk not receiving inhaled corticosteroids. These findings suggest a potential for early use of dual bronchodilators to help optimise therapy in this patient group.