This study aimed to analyse the effectiveness of an intervention for the nursing diagnosis of ineffective airway clearance in asthmatic children. A blinded, randomized and controlled clinical trial was developed in a paediatric hospital located on northeast of Brazil with 42 asthmatic children aged ≤ 36 months. The children were randomly divided into two groups (intervention and control) by means of a simple drawing. The applied intervention included actions related to change of positioning and stimulation of cough. The main findings of this study show that before the intervention, no significant difference was observed in the health status of the children. After the intervention, the indicators of choking (16.83 vs. 26.17, P = 0.007) and adventitious breath sounds (16.4 vs. 26.6, P = 0.005) were higher, on average, in the intervention group. It was observed an improvement in obstructive symptoms in children who received the intervention proposed.