Background: Caring for patients with advanced or terminal diseases can confront family caregivers (FC) with ethical challenges. The present study aims at tracing paths connected to ethical challenges among FC of advanced cancer patients by exploring morally troubling situations and related burden, as well as strategies to handle the situation and experience of moral distress from the grieving FC's perspective. Methods: Within a qualitative design, interviews with 12 grieving FC were conducted using a semi-structured interview guide. Data were analysed using grounded theory and abductive reasoning. Results: Core phenomena identified were two paths connected to ethical challenges among FC. Ethical challenges occurred in the context of difficult decision-making (Path 1) and in the context of lacking decision-making options when no decision was to be made by FC (Path 2). We found each path to be triggered by distinct sets of morally troubling situations that occurred during the patient's disease trajectory. In the course of difficult decision-making (Path 1), detrimental external factors could add emotional stress, thus making the decision-making process burdensome. FC used various proactive strategies to overcome those detrimental factors and/or to make the decision. Decisions in conflict with FCs' own moral expectations and values led to moral distress, generating painful emotions. When no decision was to be made by FC (Path 2), FC felt powerless and overrun, which was associated with major emotionality in terms of anxiety and confusion. Either detrimental factors aggravated these feelings to paralyzing shock, or internal resources enabled FC to accept the situation. While acceptance prevented moral distress, paralyzing shock often caused a sense of not meeting their their own moral expectations and values, resulting in moral distress. In both paths, factors were identified that helped FC finding closure and prevented moral residue. Nevertheless, some FC experienced residual moral distress months after the morally troubling situation had occurred. Conclusion: Findings provide first information towards understanding paths leading to ethical challenges in FC and can help clinicians to minimize associated emotional burden and moral distress.