Effects of mobile text messaging on breast cancer and breast self-examination (BSE) knowledge, BSE selfefficacy, and BSE frequency: a randomised controlled trial Aims: Educating women regarding breast cancer and increasing breast self-examination uptake continues to remain a major challenge despite the intensive campaigns. An innovative, cost-effective and easily customised intervention is needed especially in underresourced and hard to reach communities. This paper is a report examining the effects of mobile text messaging on women's knowledge of breast cancer and BSE, BSE selfefficacy and frequency of BSE. Methods: A randomised controlled trial design was used. The study sample consisted of 128 women of reproductive age (WRA) (64 in the experimental group and 64 in the control group) from two communities in the Philippines during the months of August to October 2018. Three to five short messages were sent to the participants in the experimental group daily for one month while the control group did not receive the messages. Results: Women who received mobile text messages had higher knowledge of breast cancer (F = 21.756, p = 0.001) and breast self-examination (F = 6.776, p = 0.010) than the control group. However, no significant improvements were seen in the BSE self-efficacy (F = 1.446, p = 0.232) and frequency of BSE (F = 3.374, p = 0.69). Conclusion: Mobile text messaging significantly improved the knowledge on breast cancer and breast self-examination among women; however, it did not affect their breast self-examination self-efficacy and frequency. Mobile text messaging can be a viable tool that can be used by healthcare workers in order to educate women regarding breast cancer and breast self-examination.