Adoption research shows a growing interest in adopted persons in their adult years. This article examines couple partnerships and divorce among adult adoptees and non-adoptees. Using population-based Swedish register data with follow-up until age 36–45 years, domestic and international adoptees were compared with the general population, as well as with immigrants who settled in Sweden in their early years and share with international adoptees a non-European physical appearance. Given their preadoption adversities and associated increased mental health problems, as well as postadoption experiences of perceived discrimination, adoptees were expected to have more problems in the formation and breakdown of partner relationships, particularly in the case of international adoptees. The study used data from national registers on Swedish national cohorts born 1972–83, including two study groups with a non-European origin who settled in Sweden at age 0–8 years (14,761 international adoptees and 11,085 immigrants) as well as 906 domestic adoptees and 936,988 Swedish born with a Swedish-born mother from the general population. In contrast with international adoptees, who have a 14 % lower adjusted rate of couple compared with the general population, domestic adoptees were more like the Swedish general population in terms of couple partnership formation. However, in terms of divorce, domestic and international adoptees share a significantly higher incidence than the general population and the immigrants study groups. Both in the formation and breakdown of couple relationships, international adopted men present less favorable outcomes than international adopted women. Further research is needed to elucidate the reasons behind these patterns.