How and with whom young adults live is associated with their socioeconomic status. Migration experience further shapes preference and opportunity in choosing one's living arrangement. Given limited literature on immigrant young adults living arrangements especially in a comparative perspective, this paper investigates the issue comparing Spain and the United States. Based on the 2000 US Census and the 2001 Spanish Census, the paper compares four forms of living arrangements (living alone, living with parents, living with a partner/spouse, and living in an extended family) between immigrants and the native-born and among immigrants in the two destination contexts. We focus on the role of age at migration and country of birth in living arrangements. The sample includes young adults aged 18-35 years and in the case of immigrants: those who migrated at age 1-16 years (n=518,882 natives and 7,620 immigrants in Spain; 1,836,401 natives and 192,205 immigrants in the United States). Using multinomial logistic regression and controlling for demographic and socioeconomic characteristics, it is found that immigrants' living arrangements are more similar to those of the natives than to those of the same immigrant group in the other destination country. Immigrant young adults in Spain have more similar living arrangements to the native-born in Spain than to their fellow immigrants in the United States. There remains however substantial variation by age at migration and country of birth, with those migrated at young age and those born in Western Europe having the most similar living arrangements to the natives both in Spain and the United States.