Background and objective Inspiratory muscle training (IMT) enhances velocity of inspiratory muscle contraction and modifies inspiratory and expiratory time. This study aimed to examine the impact of high-intensity IMT (H-IMT) on exercise capacity in bronchiectasis. Methods Forty-five patients were included. Lung function, respiratory muscle strength and endurance, exercise capacity, dyspnoea, fatigue and quality of life (QOL) were evaluated. Patients were randomized into two groups: H-IMT and control groups. Twenty-three patients underwent H-IMT for 8 weeks, using threshold loading with a target workload of maximal inspiratory pressure (MIP) of at least 70%, with 3-min cycles (as 2-min training: 1-min rest intervals) for 21 min. There was a total period of 14 min of loaded breathing and 7 min of recovery. The control group (n = 22) underwent low-intensity IMT at 10% of the initial MIP and was maintained at the same intensity until the end of the training. Results After training, both MIP and maximal expiratory pressure (MEP) and the incremental shuttle walk distance were increased in the H-IMT group compared with the control group (P < 0.05). There was a significant difference in constant threshold load, time and pressure-time units in the H-IMT group (P < 0.05) but not in the control group (P > 0.05). A significant decrease was found in fatigue in both groups (P < 0.05). The Leicester Cough Questionnaire social score for the H-IMT group decreased significantly after the treatment (P < 0.05). Conclusion The H-IMT increased exercise capacity in patients with non-cystic fibrosis bronchiectasis. It has also positive effects on respiratory muscle strength and endurance, and social aspects of QOL.