Prior work has not tested the basic theoretical notion that informant discrepancies in reports of children’s behavior exist, in part, because different informants observe children’s behavior in different settings. We examined patterns of observed preschool disruptive behavior across varying social contexts in the laboratory and whether they related to parent-teacher rating discrepancies of disruptive behavior in a sample of 327 preschoolers. Observed disruptive behavior was assessed with a lab-based developmentally sensitive diagnostic observation paradigm that assesses disruptive behavior across three interactions with the child with parent and examiner. Latent class analysis identified four patterns of disruptive behavior: (a) low across parent and examiner contexts, (b) high with parent only, (c) high with examiner only, and (d) high with parent and examiner. Observed disruptive behavior specific to the parent and examiner contexts were uniquely related to parent-identified and teacher-identified disruptive behavior, respectively. Further, observed disruptive behavior across both parent and examiner contexts was associated with disruptive behavior as identified by both informants. Links between observed behavior and informant discrepancies were not explained by child impairment or observed problematic parenting. Findings provide the first laboratory-based support for the Attribution Bias Context Model (De Los Reyes and Kazdin 2005), which posits that informant discrepancies are indicative of cross-contextual variability in children’s behavior and informants’ perspectives on this behavior. These findings have important implications for clinical assessment, treatment outcomes, and developmental psychopathology research.