Introduction Mobile apps are software programmes that run on smartphones and other mobile devices. Mobile health apps can help people manage their own health and wellness, promote healthy living and gain access to useful information when and where they need it. The Brush DJ oral health app was developed to use the opportunity mobile apps offer to motivate an evidence-based oral hygiene routine. A literature review has found no research investigating the use of a mobile app to motivate evidence-based oral hygiene behaviour.Objective The objective of this preliminary investigation was to assess user perception of an oral health app to give a basis for future research and development of app technology in relation to oral health.Method A cross-sectional qualitative user perception questionnaire.Results One hundred and eighty-nine people responded to the questionnaire. Seventy percent (n = 113) of respondents reported that their teeth felt cleaner since using the app. Eighty-eight percent (n = 133) reported the app motivated them to brush their teeth for longer and 92.3% (n = 144) would recommend the app to their friends and family. Four broad themes relating to how the app helped toothbrushing were reported. These themes were motivation, education, compliance and perceived benefits.Conclusion A mobile app is a promising tool to motivate an evidence-based oral hygiene routine.