Older women with primary operable breast cancer might receive suboptimal care due to their advanced age. Although several studies reported age as an independent determinant for receiving none or less treatment according to accepted standards, prospective data are lacking. This study evaluates the adherence to a consensus protocol in unselected women aged 80 years and older in the Netherlands. Data were derived from the Dutch population-based Cancer Registry held by the Comprehensive Cancer Centre East. In this study all female patients, 60 years and older, diagnosed with breast cancer TNM stage I–IIIa in the period 2001 until 2006 were selected. Applied treatment according to the Dutch guideline was compared for different age groups. Differences between age groups were evaluated using a chi-square test. In total, 2336 breast cancer patients were studied. Treatment adherence was significantly lower for surgery, radiation therapy and systemic therapy in women aged 80 years and older, and all modalities were applied much less frequently, except for endocrine therapy which was more frequently applied in the oldest old. This study shows a sharp decline in guideline adherence for unselected women aged 80 years and older with primary operable breast cancer, with an observed shift from appropriate locoregional treatment toward endocrine therapy. Whether this approach is justified or not should preferably be tested prospectively.