<h3>Background</h3> We evaluated the effect of once-daily tiotropium Respimat^® 5 µg on lung function, asthma exacerbation and asthma symptom control among patients with symptomatic asthma receiving inhaled corticosteroids (ICS; ≥800 μg/day budesonide or equivalent) + long-acting β₂-agonist (LABA). <h3>Methods</h3> Data were pooled from two replicate, double-blind, placebo-controlled, 48-week, parallel-group studies of once-daily tiotropium 5 µg versus placebo, both delivered via the Respimat^® SoftMist™ inhaler (PrimoTinA-asthma^®: NCT00772538, NCT00776984). Eligible patients had: ≥5-year history of asthma diagnosed before the age of 40 years; seven-question Asthma Control Questionnaire (ACQ-7) score of ≥1.5; experienced ≥1 exacerbation during the previous year. Patients were either lifelong non-smokers, or ex-smokers (&lt;10 pack-years) who quit smoking ≥1 year before study enrolment. Exclusion criteria included diagnosis of chronic obstructive pulmonary disease. Co-primary end points in individual trials: peak forced expiratory volume in 1 second (FEV₁) within 3 h post-dose (0–3 h) and trough FEV₁. A co-primary end point in pooled data was time to first severe exacerbation; secondary end points included time to first episode of asthma worsening and ACQ-7 response. <i>Post hoc</i> efficacy analyses were performed. <h3>Results</h3> 912 patients were randomised to receive tiotropium Respimat^® (n = 456) or placebo Respimat^® (n = 456). At Week 48, tiotropium Respimat^® was associated with statistically significant improvements versus placebo Respimat^® in peak FEV_1(0–3h) (adjusted mean difference 100 mL; 95% confidence interval: 52, 148; p &lt; 0.0001) and trough FEV₁ (adjusted mean difference 62 mL; 95% confidence interval: 18, 106; p = 0.006). Time to first severe asthma exacerbation was significantly longer with tiotropium Respimat^® versus placebo Respimat^® (282 vs 226 days, respectively; hazard ratio 0.79; p = 0.034), as was time to first episode of asthma worsening (315 vs 181 days, respectively; hazard ratio 0.69; p &lt; 0.0001). At Week 24, ACQ-7 responder rate was significantly higher with tiotropium Respimat^® (53.9%) versus placebo Respimat^® (46.9%; odds ratio 1.32; p = 0.0427). <h3>Conclusion</h3> Once-daily tiotropium Respimat^® add-on to ICS + LABA improves lung function, reduces risk of severe asthma exacerbation and asthma worsening, and significantly improves asthma symptom control compared with placebo Respimat^® in patients with symptomatic asthma.