Objective: Despite there is evidence linking romantic attachment to adjustment to divorce and separation (ADS), the mechanisms explaining this association needs further exploration. Hence, the aim of the study was to examine the mediating role forgiveness of the former partner in this association. Method: The sample was composed of 1008 divorced or separated individuals (55.5% women; M = 38.71, SD = 12.25) from Chile. Participants completed the Experiences in Close Relationships Scale to measure romantic attachment, the Questionnaire of Forgiveness in Divorce and Separation to evaluate forgiveness of the former partner, and the Psychological Adjustment to Separation Test to measure the adjustment to divorce and separation. Results: Using structural equation modeling, mediational analyses revealed that attachment anxiety was both directly and indirectly associated to ADS through forgiveness (indirect effects: loneliness = 0.08, p < 0.001, 95% CI [0.029, 0.107]; attachment to the former partner = 0.06, p < 0.001, 95% CI [0.018, 0.104]), whereas attachment avoidance had only a direct effect on ADS. Multigroup analysis revealed that this pattern of relationships was invariant across gender. Conclusions: These results highlight the role that attachment and forgiveness play in the process of adjusting to a relationship dissolution that may be useful for clinical work with separated individuals or parents.