To test a stress-diathesis model of adjustment to separation, the current study describes the trajectories of different aspects of separation adjustment in people formerly married or cohabiting, and moderators of those trajectories. A convenience sample of 303 recently separated individuals (169 women; 134 men) completed assessments of their emotional attachment to the former partner, loneliness, psychological distress, and coparenting conflict at two time points 6 months apart. Multilevel modeling of the overlapping multicohort design was used to estimate the trajectories of these different aspects of adjustment as a function of time since separation, marital status, gender, presence of children from the relationship, who initiated separation, social support, and anxious attachment. Attachment to the former partner, loneliness, and psychological distress were initially high but improved markedly across the 2 years after separation, but coparenting conflict was high and stable. Adjustment problems were similar in men and women, and in those formerly married or cohabiting, except that reported coparenting conflict was higher in men than women. Low social support and high anxious attachment predicted persistent attachment to the former partner, loneliness, and psychological distress. Coparenting conflict is a common, chronic problem for many separated individuals, and individuals with certain psychological vulnerabilities also experience chronic personal distress.