Introduction A recent meta-analysis provided proof of efficacy for mobile technology to increase physical activity or weight loss in the short term. Videoconferencing may also be effective, especially as it reduces the barriers related to face-to-face physical activity interventions. Both technologies seem particularly interesting for bariatric surgery management, but their long-term effects on physical activity maintenance are unknown. Moreover, the mechanisms underlying their effectiveness, such as technology acceptability and motivational processes, have not been examined. The objectives of this study are to determine the effects of two technology-based (mobile technology and videoconferencing) physical activity programmes after bariatric surgery compared with standard care and to assess the contribution of acceptability and motivational mechanisms in explaining these effects on physical activity, physiological measures and health indicators. Methods and analysis One hundred and twenty young women who have undergone bariatric surgery in the last 3–6 months will be included. The volunteers will be randomly assigned to one of three arms: CONTROL (standard care), ACTI-MOBIL (mobile technology) or ACTI-VISIO (videoconferencing). The primary outcome is the distance travelled during a 6 min walk test relativised according to Capadaglio’s theoretical distance. Secondary outcomes are behavioural measures of physical activity, physiological measures, health indicators, technology acceptability and motivational concepts. Data will be collected at baseline (T0), 3 months (T3) and 6 months (T6). The technology groups will receive a physical activity programme for 12 weeks (between T0 and T3). A mixed model approach will be used to analyse the change in outcomes over time for each group. Ethics and dissemination This study protocol was reviewed and approved by the French East 1 Protection of Persons Ethics Committee (number: 2020.A00172-37) and the French National Commission for Information Technology and Civil Liberties (number: UCA-R20-034). The results will be disseminated through conference presentations and peer-reviewed publications. Trial registration number NCT04478331 .