Forgiveness is crucial for emotional wellbeing and good mental health. It is therefore important to understand what cognitive processes may promote forgiveness to achieve optimal outcomes for individuals. There is some evidence to suggest that core self-evaluation (CSE) is related to how forgiving an individual may be. However, these studies have shown that this influence may be mediated by other cognitive processes. To date, the combined role of anger rumination and mindfulness as potential mediators has not been considered. This is despite recognized associations with constructs that underly CSE. To address this gap in knowledge, this study aimed to explore the relationship between CSE and forgiveness; considering whether this relationship is mediated by mindfulness and anger rumination. A further contribution to knowledge was that these relationships were considered across the three subtypes of forgiveness: self, others, and situation. A total of 490 participants (54% men; 45% women; 1% non-binary; average age = 43.7 years; SD = 17.7) provided complete responses to an online questionnaire measuring CSE, forgiveness, mindfulness, and anger rumination. The results demonstrated that CSE was positively related to forgiveness and mindfulness and negatively related to anger rumination. Mediation analysis demonstrated that some of the influence of CSE on forgiveness was through mindfulness and anger rumination. These results indicate that people with higher levels of CSE tend to have a greater degree of mindfulness, are less likely to engage in anger rumination, and are subsequently more likely to be forgiving. These findings provide further insight into the beliefs and processes that contribute to an individual's willingness to forgive. It also suggests that interventions targeting CSE, mindfulness, and anger rumination can help with the promotion of forgiveness.