Extended and underlying data (supplementary materials) to the manuscript of the research paper entitled Development and modelling study of an evidence-based manualised intervention: PErsonalised Treatment packages for Adults with Learning disabilities who display aggressive challenging behaviour in community settings (PETAL).The PETAL therapy was designed following an extensive review of existing management provisions and was co-produced with carers with lived experience and self-advocates with an intellectual disability. A single arm multi-site modelling study was conducted in England to test the delivery and acceptability of the PETAL therapy as well as some qualitative interviews with stakeholders to explore the intervention’s fidelity and acceptability.The TIDieR (Template for Intervention Description and Replication) Checklist is recommended to be complementing reports on new interventions.The GUIDED Checklist (Guidance for reporting intervention development studies in health research) is recommended to be used as a consensus-based reporting guidance for intervention development in health research.The extended data (supplementary materials) is in a Word document format and contains five tables (i.e., Summary of intervention development through co-production meetings, PETAL intervention modules and how they map onto the Theoretical Domains Framework (TDF) domains, Implementation strategies following Normalisation Process Theory (NPT), Baseline measures collected during the modelling study, Findings from the modelling study and changes made to the PETAL therapy).The underlying data consist of the anonymised dataset from the modelling study (baseline measures) and the anonymised interview transcripts from the qualitative interviews conducted with stakeholders.