Evidence shows that current adaptation planning approaches are not always successful in generating actionable knowledge to guide implementation on the ground. There remains a persistent disconnect between the production of (physical) climate science and the implementation of practical, local, and context-specific adaptation actions. We argue for a need to incorporate “subaltern” knowledge (i.e., that which is typically labeled local, traditional, or indigenous knowledge) in climate adaptation science and practice. Building on recent comparative assessment studies, we identify limitations of current local adaptation action in its typical application of scientific knowledge and illustrate key pathways through which the subaltern can be integrated to better inform current approaches. We argue that subaltern knowledge can be a critical source of innovation and can help to broaden the adaptation solution space by enhancing both the effectiveness and the social legitimacy of actions.