Objective: Antimicrobial resistance is a global health threat perpetuated by the overprescribing of antibiotics in primary care. One strategy to reduce antibiotic use in this setting is delayed prescribing. However, several psychological factors might undermine its effectiveness. The aim of the study was to test whether different interventions aiming at helping patients to manage diagnostic uncertainty in the period of watchful waiting promote appropriate antibiotic use. Method: We conducted a preregistered online experiment (N = 690 adult participants from the United Kingdom) in which we modeled delayed prescription in a decision task with behavior-contingent incentives. Participants had either a fictional viral or bacterial infection and received interventions that aimed at facilitating symptom monitoring (i.e., passive monitoring) and engaging participants in the task (i.e., active monitoring). Results: Both interventions decreased antibiotic use when the disease was viral. Active monitoring was more efficient in decreasing antibiotic use than passive monitoring. Conclusions: The findings have practical implications for managing uncertainty and fostering appropriate antibiotic use in delayed prescribing situations.