The EU Digital Markets Act (“DMA”) contains several provisions which reflect important behavioral insights, and in particular the importance of choice architecture for end user decision-making. This article discusses three roles played by such insights. First, several DMA obligations address conduct whose anticompetitive effects arise from the interlinkage between choice architecture and end user behavior. Second, certain DMA obligations more explicitly cover the choice ar- chitecture facing users. Third, the heavy emphasis on effectiveness within the DMA creates a potential role for behavioral insights. If gatekeepers are to be effective in promoting fairness and contestability, to comply with the DMA, then they may need to do more to address behavioral biases than the provisions state explicitly “on their face.” But does the DMA go far enough in considering the implications of behavioral economics? Arguably not. This article also describes some residual questions and challenges arising where more clarity could be given or more could usefully be done.