Handover between colleagues is a complex task. The problem is that handovers are often inadequate because they are not structured according to theoretically grounded guidelines. Based on the cognitive load theory, we suggest that allowing a clarifying dialogue and thereby optimizing germane cognitive load enhances the information quality and diagnostic accuracy at handover, but may prolong handover duration. We also expect that mentioning key information first and thus decreasing intrinsic cognitive load improves information quality and diagnostic accuracy. We developed two representative paediatric cases for presentation in a factorial 2 × 2 design. Sixth-year medical students (N = 80) were randomly assigned to one of four groups that differed with regard to how the case histories were delivered to them (chronological order versus key information mentioned first) and direction of information exchange (unidirectional versus a clarifying dialogue). The receivers of the handover were asked to write a report of the cases and suggest the best diagnosis. Dependent variables were information quality of the written report (Information score), quality of the diagnosis (Diagnostic accuracy score) and the time it took to deliver the written handover case report (Handover report duration). Seen through the lens of cognitive load theory, allowing a clarifying dialogue at handover, and thus optimizing the germane cognitive load, significantly increased the Information score (p < 0.0005), Diagnostic accuracy score (< 0.05) and Handover report duration (p < 0.001).