Objectives: Out-of-hospital cardiac arrest has poor prognosis and patients rarely survive unless they receive immediate cardiopulmonary resuscitation from bystanders. In 2012, the British Heart Foundation launched its PocketCPR training application to simplify bystander cardiopulmonary resuscitation training and overcome barriers to resuscitation. This study investigates whether the British Heart Foundation PocketCPR training application improves the confidence of bystanders who perform cardiopulmonary resuscitation during simulated resuscitation attempts. Methods: This is a mixed method study using a randomised crossover trial with questionnaire analysis. One hundred and twenty participants were randomised to either perform two minutes of cardiopulmonary resuscitation on a resuscitation manikin using the British Heart Foundation PocketCPR application or perform cardiopulmonary resuscitation without instruction. Participants completed a questionnaire to capture their confidence before completing the opposite arm of the study. Each participant then completed a second questionnaire to allow for comparison of levels of confidence. Results: Participants in this study were more confident in their overall performance of cardio- pulmonary resuscitation using the British Heart Foundation PocketCPR training application compared to performing cardiopulmonary resuscitation without instruction (mean confidence score (0–100): 50.41 with PocketCPR and 43.92 without (p = 0.026)). They were also more confident that the number of chest compressions in this study was correct (mean: 60.39 with PocketCPR vs. 46.10 without (p < 0.001)), and in the delivery of cardiopulmonary resuscitation without havingrecent cardiopulmonary resuscitation training (mean: 48.67 with PocketCPR vs. 39.79 without (p < 0.002)). Conclusion: The British Heart Foundation PocketCPR training application improved the confi- dence of bystanders performing cardiopulmonary resuscitation during simulated resuscitation attempts.