To date, several theoretical models have been proposed to explain how the expected and natural grief processes turns into psychiatric disorders. Nevertheless, there is a paucity of empirical research examining the basic assumption of psychoanalytic theory regarding pre-death conflict and bereavement related guilt. Accordingly, the current study aimed to investigate the mediator role of bereavement related guilt in the relationship between the pre-death conflict and maladaptive grief process. The sample consisted of 447 bereaved adults who lost a loved one due to death in the last 5 years. The Unfinished Business in Bereavement (UBBS), Bereavement Guilt Scale (BGS), Beck Depression Inventory (BDI), and Prolonged Grief Disorder Scale (PG-13) scales were administered. The results indicated that the UBBS scores were positively correlated with both BDI and PG-13 scores, and BGS scores mediated these relationships. Obtained findings were discussed in relation to psychoanalytic theory and existing studies in the grief literature.