Breathing retraining (BR) improves symptoms, psychological well-being and quality of life in adults with asthma; but there remains uncertainty as to mechanism of effect. One of the intuitively logical theories is that BR works through altering breathing pattern. There is currently no evidence, however, that BR does result in measurable changes in breathing pattern. In this case report we describe the effects of physiotherapy BR on a 57-year-old female with a 10-year history of asthma. Data were collected before and after a physiotherapy BR program comprising three sessions over 18 weeks: breathing pattern (respiratory inductive plethysmography (RIP); physiology (end tidal carbon dioxide (ETCO2), heart rate, oxygen saturations, spirometric lung function); questionnaires (Asthma Control Questionnaire (ACQ), Hospital Anxiety and Depression Score, Nijmegen Questionnaire); and medication usage. After BR, the patient's symptoms improved. Her physiology was largely unchanged, although her FEV1 increased by 0.12L, peak flow by 21L/min. The patient reported using less Salbutamol, yet her asthma control improved (ACQ down 1.5). Her Nijmegen score dropped from positive to negative for hyperventilation (from 39 to 7). Her anxiety-depression levels both reduced into 'normal' ranges. The patient's expiratory time increased, with longer respiratory cycles and slower respiratory rate. No changes were seen in relative contributions of ribcage and abdomen. Controlled trials are now needed to determine the generalizability of these findings.