Background: The process of forgiveness is proposed to reduce patient and family conflict and suffering in the face of life-limiting illness. However, it is unclear which theoretical perspectives underpin the concept of forgiveness in palliative care, and how culture may influence it. Objectives: To identify and synthesize primary evidence that underpins the concept of forgiveness within palliative care, and identify theoretical perspectives, including cultural assumptions. Design: A systematic review of studies on forgiveness in palliative care regardless of design was prospectively registered on PROSPERO. Narrative synthesis was conducted and the modified Seven-Point Checklist and modified Status Assessment Tool applied to appraise study quality (level 1) and contributions to theory building (level 2). Data Sources: Reference chaining and hand-searching were conducted for 10 electronic databases from 1960 to June 30, 2020. Results: Thirty-nine studies were included. Seven provided a definition of forgiveness, and six studies reported a process model. Twelve patient studies scored "high" on quality level 1 and nine scored "high" on level 2. Conceptualization of forgiveness included a conscious decision to abandon negative thoughts, feelings, and behaviors associated with conflicts, to find positive outcomes through processing of negative affect and cognitive reframing of conflicts. The process of forgiveness develops through time paralleled by an attributional movement from an external to an internal locus of control. Theoretical perspectives of systems, exchange and choice, social constructionism, behaviorism, and humanism were identified. Cultural contexts impact forgiveness. Conclusion: The synthesized model is based on primary evidence of mixed quality. Future research needs better theoretical conceptualization utilizing cultural perspectives. Forgiveness interventions with consideration of cultural influences are encouraged.