This study explores the link between peer problems in school and contextual variations in negative mood and state self-esteem over a 5-day period. Fifth-grade children completed measures of mood and state self-esteem while they were at home in the morning and while they were at school each day, allowing for an examination of whether psychological states change from context to context and whether these changes are influenced by types of peer events that children report experiencing at school. Results indicated that children who experienced more peer problems at school showed, on average, a shift toward more negative mood and lowered state self-esteem from mornings at home to afternoons at school during the week of data collection. Peer problems were also associated with higher levels of negative mood at school after controlling for academic problems but no longer predicted state self-esteem in school when academic problems were controlled. (Contains 4 tables, 1 figure, and 1 note.)