Abstract Background Palliative care is becoming increasingly important because the number of patients with an incurable disease is growing and their survival is improving. Previous research tells us that early palliative care has the potential to improve quality of life (QoL) in patients with advanced cancer and their relatives. According to limited research on palliative care in the Netherlands, patients with advanced cancer and their relatives find current palliative care suboptimal. The aim of the eQuiPe study is to understand the experienced quality of care (QoC) and QoL of patients with advanced cancer and their relatives to further improve palliative care. Methods A prospective longitudinal observational cohort study is conducted among patients with advanced cancer and their relatives. Patients and relatives receive a questionnaire every 3 months regarding experienced QoC and QoL during the palliative trajectory. Bereaved relatives receive a final questionnaire 3 to 6 months after the patients’ death. Data from questionnaires are linked with detailed clinical data from the Netherlands Cancer Registry (NCR). By means of descriptive statistics we will examine the experienced QoC and QoL in our study population. Differences between subgroups and changes over time will be assessed while adjusting for confounding factors. Discussion This study will be the first to prospectively and longitudinally explore experienced QoC and QoL in patients with advanced cancer and their relatives simultaneously. This study will provide us with population-based information in patients with advanced cancer and their relatives including changes over time. Results from the study will inform us on how to further improve palliative care. Trial registration Trial NL6408 (NTR6584). Registered in Netherlands Trial Register on June 30, 2017.