Prolonged grief is a chronic and debilitating condition that affects millions of persons worldwide. The aim of this study was to use a qualitative approach to better understand how relatives with prolonged grief disorder perceive what does or not help them and whether they were able to make recommendations. Participants were all relatives of deceased patients admitted to 26 palliative care units involved in the FamiLife study; relatives were included if diagnosed with prolonged grief symptoms (i.e., Inventory Complicated Grief (ICG) questionnaire with a cut-off >25), and volunteered to participate. Semi-directed telephone interviews were conducted by psychologists between 6 and 12 months after the patient's death. The interviews were open-ended, without a pre-established grid, then transcribed and analyzed using a thematic approach. Overall, 199/608 (32.7%) relatives were diagnosed with prolonged grief symptoms, i.e., with an ICG score >25, and 39/199 (20%) agreed to be interviewed. The analysis yielded 4 themes: (1) the experience of mourning: intense sadness and guilt (reported by 35/39 participants, 90%); (2) aggravating factors (38/39, 97%): feeling unprepared for death and loneliness, presence of interpersonal barriers to adjustment, external elements hindering the mourning progress; (3) facilitating factors (39/39, 100%): having inner strength or forcing oneself to get better, availability of social and emotional support; and (4) the suggestions grieving relatives had to alleviate the grief burden (36/39, 92%). The analysis enabled to identify 5 suggestions for relieving the grief burden: improving communication, developing education about death and grief, maintaining contact, offering psychological support, and choosing the right time for the palliative care team to contact the relatives. This study revealed how bereaved relatives experienced the help provided by the healthcare teams, their representations, and what could be improved. These findings could be used to design intervention studies.