Researchers and practitioners conduct multi-informant assessments of child and family behavior under the assumption that informants have unique perspectives on these behaviors. These unique perspectives stem, in part, from differences among informants in the settings in which they observe behaviors (e.g., home, school, peer interactions). These differences are assumed to contribute to the discrepancies commonly observed in the outcomes of multi-informant assessments. Although assessments often prompt informants to think about setting-specific behaviors when providing reports about child and family behavior, the notion that differences in setting-based behavioral observations contribute to discrepant reports has yet to be experimentally tested. We trained informants to use setting information as the basis for providing behavioral reports, with a focus on parental knowledge of children’s whereabouts and activities. Using a within-subjects controlled design, we randomly assigned 16 mothers and adolescents to the order in which they received a program that trains informants to use setting information when providing parental knowledge reports (Setting-Sensitive Assessment), and a control program involving no training on how to provide reports. Relative to the control program, the Setting-Sensitive Assessment training increased the differences between mother and adolescent reports of parental knowledge, suggesting that mothers and adolescents observe parental knowledge behaviors in different settings. This study provides the first experimental evidence to support the assumption that discrepancies arise because informants incorporate unique setting information into their reports.