Prior research has identified the similarity of Action Research (AR) and Design Science Research (DSR). This paper analyses AR and DSR from several perspectives, including paradigmatic assumptions of ontology, epistemology, methodology, and ethics, their research interests, and activities. We identify that often AR does not share the paradigmatic assumptions and the research interests of DSR, that some activities in DSR are always mutually exclusive from AR, and that there may be no, little, or significant (but not total) overlaps between AR and DSR. Thus we judge that AR and DSR are decisively dissimilar. We further identify several key problems with combining AR and DSR based on the ethical requirement of researchers to identify and manage risks to research stakeholders. Management of such risks is done by careful disclosure, identifying research limitations or by choosing alternative methods than AR for accomplishing DSR.