Introduction: Although adolescents make treatment gains in psychiatric residential treatment (RT), they experience significant difficulty adapting to the community and often do not sustain treatment gains long term. Their parents are often not provided with the necessary support or behaviour management skillset to bridge the gap between RT and home. Parent training, a gold standard behaviour management strategy, may be beneficial for parents of these youth and web-based parent training programmes may engage this difficult-to-reach population. This study focuses on a hybrid parent training programme that combines Parenting Wisely (PW), a web-based parent training with facilitated discussion groups (Parenting Wisely for Residential Treatment (PW RT )). This study aims to: (1) establish the feasibility and acceptability of PW RT , (2) evaluate whether PW RT engages target mechanisms (parental self-efficacy, parenting behaviours, social support, family function) and (3) determine the effects of PW RT on adolescent outcomes (internalising and externalising behaviours, placement restrictiveness)., Methods and Analysis: In this randomised control trial, parents (n=60) will be randomly assigned to PW RT or treatment as usual. Each week for 6 weeks, parents in the PW RT condition will complete two PW modules (20 min each) and attend one discussion group via Zoom (90 min). Adolescents (n=60) will not receive intervention; however, we will evaluate the feasibility of adolescent data collection for future studies. Data from parents and adolescents will be collected at baseline, post intervention (6 weeks post baseline) and 6 months post baseline to allow for a robust understanding of the longer-term effects of PW RT on treatment gain maintenance., Ethics and Dissemination: The study has been approved by The Ohio State University Institutional Review Board (protocol number 2022B0315). The outcomes of the study will be shared through presentations at both local and national conferences, publications in peer-reviewed journals and disseminated to the families and organisations that helped to facilitate the project., Trial Registration Number: NCT05764369 (V.1, December 2022)., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)