Purpose: The purpose of this study was to investigate variables and construct paths that affect complicated grief. Methods: Participants in this cross-sectional, descriptive study were 164 bereaved spouses of cancer patients at least 12 months before the death. Data were collected from October 2016 to February 2017 using self-report structured questionnaires and were analyzed using IBM SPSS 21.0 and AMOS 20.0. Results: The variables affecting complicated grief of bereaved spouses of cancer patients were the quality of end-of-life care (g=.15, pqqqlt;.001), preparedness for death (b=-.06, p=.005), and coping with bereavement (b=-.24, pqqqlt;.001), whereas the quality of death and dying did not show any effects. Preparedness for death had multiple mediating effects in the relationship between the quality of end-of-life care and complicated grief (z=-2.20, p=.028), and in the relationship between the quality of end-of-life care and coping with bereavement (z=2.11, p=.035). Coping with bereavement had a mediating effect on the relationship between preparedness for death and complicated grief (z=-2.39, p=.017). Conclusion: This study revealed that preparedness for death and coping with bereavement play a prominent role in complicated grief. Therefore, it is important to help in preparing for death and enhancing coping with bereavement of spouses providing end-of-life care to cancer patients. In addition, investigating cultural differences in the relationship between the quality of end-of-life care and complicated grief is recommended.