The self-management of asthma can improve clinical outcomes. Recently, mobile telephones have been widely used as an efficient, instant personal communication tool. This study investigated whether a self-care system will achieve better asthma control through a mobile telephone-based interactive programme. This was a prospective, controlled study in outpatient clinics. From 120 consecutive patients with moderate-to-severe persistent asthma, 89 were eventually recruited for the study, with 43 in the mobile telephone group (with a mobile telephone-based interactive asthma self-care system). In the mobile telephone group, mean ± sem peak expiratory flow rate significantly increased at 4 (378.2 ± 9.3 L·min⁻¹; n = 43; p = 0.020), 5 (378.2 ± 9.2 L·min⁻¹; n = 43; p = 0.008) and 6 months (382.7 ± 8.6 L·min⁻¹; n = 43; p = 0.001) compared to the control group. Mean±sem forced expiratory volume in 1 s significantly increased at 6 months (65.2 ± 3.2% predicted; n = 43; p < 0.05). Patients in the mobile telephone group had better quality of life after 3 months, as determined using the Short Form-12® physical component score, and fewer episodes of exacerbation and unscheduled visits than the control group. Patients in the mobile telephone group significantly increased their mean daily dose of either systemic or inhaled corticosteroids compared with the control group. The mobile telephone-based interactive self-care system provides a convenient and practical self-monitoring and -management of asthma, and improves asthma control.