The working routines in palliative care nursing are associated with a variety of causes of stress with regional and setting-specific differences in Germany. This mixed-methods study aimed to investigate the mental and physical well-being among nurses in German palliative and hospice care and to gain a deeper understanding of procedural and structural aspects that may influence the mental and physical burden in palliative nursing care. The mixed-methods approach combined qualitative interviews, (n = 16) an online survey (n = 101), and subsequent data validation in a focus group (n = 6). Interview and focus group data were analysed using structured qualitative content analysis. Survey data were analysed using descriptive statistics and an explorative quantitative analysis. Moderate to very high levels of stress were reported across all settings, but were highest for nurses in specialized outpatient palliative care settings. Underlying causes of stress related to working conditions in the nursing profession across all palliative care settings were poor working hours, perceived inadequate remuneration, and high demands for documentation. To ensure sustainable high-quality palliative care, adaptations to working conditions that target causes of stress and burden in palliative care nurses are required.