Deficits in social cognition may impair the ability to negotiate social transactions and relationships and contribute to socio emotional difficulties experienced by some post-institutionalized children. We examined false belief and emotion understanding in 40 institutional care-adopted children, 40 foster care-adopted children and 40 birth children. Both groups of adopted children were adopted internationally. Controlling for verbal ability, post-institutionalized children scored lower than birth children on a false belief task. Almost half of the post-institutionalized children performed below chance levels. The foster care group did not differ from either group on false belief understanding. The groups did not differ on emotion understanding after controlling for verbal ability. The results suggest that some post-institutionalized children are delayed in false belief understanding.