Aerobika oscillating positive expiratory pressure (OPEP) device promotes airway clearance in many respiratory diseases. However, studies have yet to focus on its effectiveness in improving small airway resistance impulse oscillometry (IOS) measurement in COPD subjects. We aim to evaluate the improvement of small airway resistance ( IOS), lung function (spirometry), exercise capacity 6-min walking test (6MWT), symptoms COPD assessment test (CAT) and severe exacerbation events among COPD subjects using Aerobika OPEP. This was a prospective, single-arm interventional study among COPD subjects with small airway disease. Subjects were instructed to use twice daily Aerobika OPEP (10 min each session); for 24 weeks; as an additional to standard therapy. IOS, spirometry, 6MWT, CAT score and severe exacerbation events were evaluated at baseline, 12 weeks and 24 weeks. Fifty-three subjects completed the study. Aerobika usage showed improvement of IOS parameters; e.g. measurement of airway resistance at 5 Hz (R5), cmH20/L/s, (12-week  = 0.008, 24-week  < 0.001), R5% predicted (12-week  = 0.007, 24-week  < 0.001) and small airway resistance (R5-R20), cmH20/L/s, (12-week 0.021, 24-week  < 0.001). There were improvement of lung function; e.g. FEV , L (12-week  = 0.018, 24-week  = 0.001), FEV % predicted (12-week  = 0.025, 24-week  = 0.001), FEF , L (12-week  = 0.023, 24-week  = 0.002), and FEF % predicted (12-week  = 0.024, 24-week  < 0.001). CAT score improved at 12 weeks (  < 0.001) and 24 weeks (  < 0.001). Subjects had improved exercise capacity (6MWT, metres) after 24 weeks (  = 0.016). However, there was no significant difference in severe exacerbation events 24 weeks before and after Aerobika usage. Aerobika OPEP demonstrated significant improvement in small airway resistance as early as 12 weeks of usage, with sustained improvement at 24 weeks. Aerobika OPEP administration had significantly improved lung function, 6MWT, and CAT scores over 24 weeks. There was no difference in severe exacerbation events.