Objectives In the Netherlands, a case of euthanasia of an incompetent patient with dementia and an advance euthanasia directive (AED) caused great societal unrest and led to a petition signed by more than 450 physicians. In this paper, we investigate these physicians’ reasons and underlying motives for supporting the ‘no sneaky euthanasia’ petition, with the aim of gaining insight into the dilemmas experienced and to map out topics in need of further guidance. Methods Twelve in-depth interviews were conducted with physicians recruited via the webpage ‘no sneaky euthanasia’. General topics discussed were: reasons for signing the petition, the possibilities of euthanasia in incompetent patients and views on good end-of-life care. Data were interpreted using thematic content analysis and the framework method. Results Reasons for supporting the petition are dilemmas concerning ‘sneaky euthanasia’, the over-simplified societal debate, physicians’ personal moral boundaries and the growing pressure on physicians. Analysis revealed three underlying motives: aspects of handling a euthanasia request based on an AED, good end-of-life care and the doctor as a human being. Conclusions Although one of the main reasons for participants to support the petition was the opposition to ‘sneaky euthanasia’, our results show a broader scope of reasons. This includes their experience of growing pressure to comply with AEDs, forcing them to cross personal boundaries. The underlying motives are related to moral dilemmas around patient autonomy emerging in cases of decision-making disabilities in advanced dementia. To avoid uncertainty regarding patients’ wishes, physicians express their need for reciprocal communication.