OBJECTIVE We explored the dual-task costs of climbers performing a visual communication task using a head-mounted display (HMD) while simultaneously climbing along a vertical surface. BACKGROUND Climbing is affected by secondary auditory cognitive tasks, and climbing impairs later recall of secondary task information; the effects of visually presented tasks are less clear. Given that HMDs are projected to be adopted into emergency response work, questions are raised about the effects of HMD use during climbing or other physical tasks. METHODS Climbers performed five conditions-a climbing-only condition, two dual-task climbing conditions (words presented on the HMD with and without auditory warnings while climbing), and two seated control conditions (words presented on the HMD with and without auditory warnings)-in a repeated-measures design. Motion data were also collected to examine participant motion around word presentation. RESULTS We found a decrease in both climbing performance and word recall under dual-task conditions, paralleling results found in previous research using auditory tasks. Participants slowed around word presentations on the HMD. Additional comparisons to previous research indicate that physical tasks may be more detrimental to word recall than are seated tasks and that visual stimuli might hinder climbing performance more than do audible stimuli. CONCLUSIONS Complex physical activity, like climbing, is disruptive to memory rehearsal and later recall, and cognitive tasks disrupt physical performance. CONCLUSIONS Avoiding cognitive HMD tasks requiring later recall during complex physical activity is advisable. However, these systems may be developed to provide intelligent assistance, or memory augmentation, in these settings.