Healthcare providers may feel regret when the care they provide falls short of expectations. This qualitative study solicited experiences from 29 German primary care providers about diagnostic errors resulting in delayed care or harm. In nearly all cases (26/29) the final diagnosis was more serious than the original diagnosis and one-third resulted in preventable harm to patients (e.g., regular blood glucose tests may have prevented a stroke that likely occurred due to decompensated diabetes under steroids).  Regardless whether the diagnostic error resulted in patient harm, the vast majority (27/29) of providers expressed feelings of regret, highlighting the need for peer-support to deal with the emotional impact of incorrect diagnostic decisions.