Purpose: Oral anti-cancer medications are increasingly common and endocrine therapies represent the most common oral anti-cancer medications in breast cancer. Adjuvant endocrine therapies reduce the likelihood of recurrence and mortality in the approximately 80% of women diagnosed with hormone-receptor positive breast cancer, thus rendering adherence essential. Real-time medication adherence monitors, such as the Wisepill electronic pillbox, transmit adherence data remotely, allowing for early intervention for non-adherence. However, their feasibility and acceptability have yet to be examined among breast cancer survivors taking endocrine therapies.Methods: This study presents quantitative patient-report and technical support data and qualitative patient acceptability data on using Wisepill, a common real-time adherence monitor, among 88 breast cancer survivors prescribed adjuvant endocrine therapy.Results: This mixed-methods study of a common real-time adherence monitor, among the first in breast cancer survivors taking adjuvant endocrine therapy, demonstrates its technical feasibility and patient acceptability.Conclusion: The use of wireless medication monitors that transmit real-time adherence data are uniquely promising for maximizing the benefits of adjuvant endocrine therapy by allowing for continuous tracking, ongoing communication with oncologic or research teams, and early intervention. This study demonstrates the feasibility and patient acceptability of one such real-time adherence monitor.