Purpose: The study purpose was to determine the effects on quality of life (QoL) of a mobile phone app & ndash;based training for supportive care of women with breast cancer who were using adjuvant endocrine hormonal therapy. Methods: The study is based on a randomized pre-post test design. Participants were randomly assigned to either a control group that received routine care or an intervention group that received routine care plus access to the mobile phone app & ndash;based training support for 12 weeks. QoL and symptom distress were measured before intervention (T0), and after 12 weeks (T1) of intervention. This study is the application of two modality combinations: the mobile app-based patient education (1) and web-based management application (2). The mobile app-based training also provided basic information about breast cancer, symptom diary and lifestyle recommendations (adequate and balanced nutrition, regular physical activity, deal with stress effectively). Results: QoL of the treatment group after intervention increased and distress level was lower compared to the control group; these results were statistically significant. The majority of the patients reported that the mobile application was "informative and useful". Conclusions: This demonstrated that the mobile app is an effective intervention for supportive care in women with breast cancer. The mobile app & ndash;based training, which is an innovative intervention, is recommended as a supportive care initiative for women with breast cancer.