This longitudinal study, conducted among a sample of Finnish primary-school children, examined the proposition that a single high-quality relationship (either with a teacher or a parent) can buffer against adjustment problems. Teachers rated the externalizing problems and prosocial behaviors of 378 children in Grade 1 and again in Grade 2. Relationship measures gathered in Grade 1 included teacher reports of positive affect for the child and mother reports of support for the child. The results supported our proposition by showing that for child adjustment after the transition to primary school it was critical to have at least one high-quality relationship either with a teacher or a parent. High positive teacher affect in Grade 1 buffered against adjustment problems for children with low maternal support, whereas high maternal support in Grade 1 buffered against adjustment problems for children with low positive teacher affect. In turn, children who received low support from both teachers and parents showed the poorest adjustment.