Background Projections of future trends in cancer incidence and mortality are important for public health planning. Methods By using 1976–2010 data in Hong Kong, we fitted Poisson age-period-cohort models and made projections for future breast cancer incidence and mortality to 2025. Results Age-standardised breast cancer incidence (/mortality) is projected to increase (/decline) from 56.7 (/9.3) in 2011–2015 to 62.5 (/8.6) per 100 000 women in 2021–2025. Conclusions The incidence pattern may relate to Hong Kong’s socio-economic developmental history, while falling mortality trends are, most likely, due to improvements in survival from treatment advancement and improved health service delivery