Marital infidelity, of whatever kind, causes serious conflicts in the relationship between spouses. Forgiveness is recognised as an important element in improving the relationship between spouses. It aids the conflict resolution process and increases commitment to the relationship. The aim of this study was to determine the determinants of forgiveness of infidelity in married people. A total of 373 people (339 women, 34 men), aged between 22 and 64 years, were studied. The study was conducted electronically using: Marital Forgiveness Scale (MOFS, Paleari, Regalia, Fincham, 2009; Polish adaptation Brudek, Steuden, 2015), Positivity Orientation Scale (Positivity Scale, Caprara et al., 2012; Polish adaptation Laguna, Oleś, Filipiuk, 2011), TIPI-PL (Ten Item Personality Inventory, Polish adaptation Sorokowska, Słotwińska, Zbieg, Sorokowski, 2014) and a personal questionnaire.
 The correlational analyses conducted showed a positive relationship between relationship commitment, relationship fulfilment, positive orientation and emotional stability and forgiveness in the subjects. The higher the level of forgiveness, the higher the positive orientation. The relationship between personality traits and forgiveness in people experiencing betrayal was partially confirmed. A positive relationship was shown at a weak level between benevolence and agreeableness and a negative one with conscientiousness. Fulfilment and commitment were shown to be significant predictors of forgiveness. The relationship between commitment and forgiveness is moderated by the trait conscientiousness. The adopted pattern of variables explains respectively 17% of the variation in the results of the forgiveness variable.