To assess the skill of bag-tube manual ventilation with the flow-inflating bag in multiprofessional PICU team members using a mobile simulation unit. Prospective observational study from January 2022 to April 2022. In situ mobile simulation using the flow-inflating bag in an academic PICU. Multiprofessional PICU team members including nurses, respiratory therapists, nurse practitioners, fellows, and attendings. None. We enrolled 129 participants who twice completed 1-minute tasks performing bag-tube manual ventilation with a flow-inflating bag. Sessions were video recorded; four could not be analyzed. Only 30% of participants reported being very to extremely confident, and the majority (62%) reported infrequent skill performance. Task success was defined as achieving target pressure ranges during 80% of the delivered breaths, respiratory rate (RR) of 25-35 breaths/min, and successful pop-off valve engagement. Only five of 129 participants (4%) achieved successful ventilation as defined. Overall, participants were more likely to deliver lower pressures and faster rate. Maintaining target positive end-expiratory pressure (PEEP) was least likely to be achieved (19% success), followed by RR (52%), pop-off valve (64%), then peak inspiratory pressure (71%). Nurses were less likely to achieve target pressures compared with all other professions. Multiprofessional PICU team members have highly variable self-confidence with bag-tube manual ventilation using a flow-inflating bag. Observed performance demonstrates rare success with achieving targeted ventilation parameters, in particular maintenance of PEEP. Future research should focus on developing mobile simulation units to facilitate profession-specific, real-time coaching to teach high-quality manual ventilation that can be translated to the bedside.