Microaggressions are a new moral category that refers to the subtle yet harmful forms of discriminatory behavior experienced by members of oppressed groups. Such behavior often results from implicit bias, leaving individual perpetrators unaware of the harm they have caused. Moreover, microaggressions are often dismissed on the grounds that they do not constitute a real or morally significant harm. My goal is therefore to explain why microaggressions are morally significant and argue that we are responsible for their harms. I offer a conceptual framework for microaggressions, exploring the central mechanisms used for identification and the empirical research concerning their harm. The cumulative harm of microaggressions presents a unique case for understanding disaggregation models for contributed harms, blame allocation, and individual responsibility within structural oppression. Our standard moral model for addressing cumulative harm is to hold all individual contributors blameworthy for their particular contributions. However, if we aim to hold people responsible for their unconscious microaggressions and address cumulative harm holistically, this model is inadequate. Drawing on Iris Marion Young's social connection model, I argue that we, as individual perpetrators of microaggressions, have a responsibility to respond to the cumulative harm to which we have individually contributed.