Emotional and behavioral problems (EBPs) frequently occur in young autistic children. Discrepancies between parents and other informants are common but can lead to uncertainty in formulation, diagnosis and care planning. This study aimed to explore child and informant characteristics are associated with reported child EBPs across settings. Participants were 83 4-8-year-old autistic children and their parents and teachers in the Autism Spectrum Treatment and Resilience (ASTAR) study. Questionnaires of child EBPs were completed by parents and teachers, and self-reported parenting stress and wellbeing measures were obtained. An observation of parent-child/researcher-child interaction was also completed. Parents reported more EBPs than teachers and parent-teacher agreement was low, particularly for emotional problems. Greater parenting stress and being verbal was associated with more parent- but not teacher-reported EBPs. More observed behaviors that challenge were displayed by minimally verbal children. More parenting stress could be associated with the presence of more EBPs in the home; alternatively, parenting stress may confound reports. It is essential for assessments of EBPs in autistic children to take a multi-informant approach. Better understanding of the associations between informant characteristics and informant discrepancies of EBPs is needed.