We hypothesised that applying the active cycle of breathing techniques (ACBT) in patients with acute hypercapnic respiratory failure undergoing non-invasive ventilation would improve patient outcome. Thirty-four patients were randomised so that 17 patients with acute hypercapnic respiratory failure received the ACBT and non-invasive ventilation (ACBT group), and 17 patients received non-invasive ventilation alone (control group). The primary outcome measure was length of time requiring non-invasive ventilation, and secondary outcome measures were change in acute physiology score, change in arterial blood gas values, total duration of non-invasive ventilation, and length of stay in the intensive care unit. Although not significant, there was a greater decrease in arterial carbon dioxide pressure in the ACBT group compared to the control group (-21.41 mmHg vs -17.45 mmHg, p = 0.27). Total duration of ventilation tended to be shorter in the ACBT group than in the control group (64.9 hours vs 84.1 hours, p = 0.15). Length of time in need of non-invasive ventilation was significantly lower in the ACBT group than in the control group (5.0 days vs 6.7 days, p = 0.03). There was no significant difference in length of stay in the intensive care unit between the two groups (8.0 vs 9.4 days, p = 0.31). The use of ACBT may have positive effects in the treatment of patients with acute hypercapnic respiratory failure, resulting in a shorter length of time requiring non-invasive ventilation.