Introduction Changes in risk factors and the introduction of mammography screening in 2005 have led to dramatic changes in the breast cancer-associated burden of disease in Germany. This study aimed to investigate long-term disease-related incidence and mortality trends in women from East and West Germany since the reunification of Germany. Methods Total and stage-specific incidence rates were evaluated based on data obtained from selected cancer registries. Sufficiently complete data going back to 1995 were available for 4 East German and 3 West German regions. The figures were weighted for population size, and rates were calculated for the whole of Germany based on the rates for East and West Germany. The study particularly focused on 3 different age groups: women eligible for mammography screening (50 - 69 years), younger women (30 - 49 years) and older women (70+ years). All rates were standardised for age. The mortality rates obtained from the official statistics on cause of death since 1990 were processed accordingly. Results Incidence rates in the observation period increased, as they were affected by the increasing number of cases with early-stage cancers being diagnosed in the screening age group. The total incidence for this group, which included the incidence of non-invasive breast cancers, increased by 14.5% between 2005 and 2016. Early-stage cancers (UICC stages 0 and I) increased by 48.1% while late-stage diagnoses (UICC stages III and IV) decreased by 31.6%. Qualitatively similar changes were noted for the other age groups, although they were less pronounced. The decrease in breast cancer mortality observed since the mid-1990s ended around 2008 for the group of younger women but continued in the screening age group. After 2008, an increase in mortality was observed in the group of older women. The differences in disease burden between East and West Germany (in favour of East Germany) decreased in younger women during the observation period but tended to increase in the group of older women. Conclusion The analysis suggests that the introduction of mammography screening contributed to a decrease in the incidence of advanced-stage breast cancers and in breast cancer-related mortality rates but also resulted in a substantial number of overdiagnoses. The relatively unfavourable incidence trend in the group of younger women, particularly in East Germany, should be interpreted in the context of lifestyle changes. The slight increase in mortality observed in the group of older women after 2008 requires further analysis.