Patient education is one of the important aspects of improving knowledge and quality of asthma control. In this digital era, it can be made with the support of an app – or known as mHealth. Unfortunately, implementing applications for patient education is relatively new among asthmatic patients in Indonesia. This study aimed to determine the efficacy of the educational content of the AsmaDroid® app on the levels of asthma knowledge among asthmatic patients. This study was a randomized controlled trial carried out from December 2019 to March 2020 in the Special Region of Yogyakarta, Indonesia. A quota sampling was employed, resulting in 140 study participants being categorized into control and treatment groups. Before and after the 4-week treatment period, all participants were asked to complete a pre-test and post-test of the Asthma General Knowledge Questionnaire for Adults (AGKQA) questionnaire. All the scores were then compared to determine the efficacy of educational content on the levels of asthma knowledge. The results of descriptive statistics reported that the pretest scores of AGKQA from the control group (minimum, maximum, and mean) were 9, 25, and 19.04±2.56, respectively, and post-test scores were 10, 27, and 18.79±3.59 (p=0.47). Meanwhile, in the treatment group, these were 13, 25, and 19.11±2.87, while post-test scores were 16, 31, 23.6±3.95 (p=0.01). Additionally, there was a difference between the post-test scores of the control and treatment groups, namely 4.81 (p=0.01). The educational content of the app significantly improved the levels of asthma knowledge.