BACKGROUND Background: The growing number of cancer survivors experiencing persistent physical, psychological, and social limitations is placing increasing pressure on health care systems and this requires more structured, biopsychosocial approaches to care. Oncological physiotherapy plays a key role within multidisciplinary teams; however, assessment practices remain heterogeneous, with limited standardization, unclear clinical applicability, and a lack of consensus on appropriate measurement instruments despite existing conceptual frameworks. OBJECTIVE Objective: This study aims to develop an evidence-informed, consensus-based framework (IN-GUIDE) for the selection, prioritization, and implementation of assessment instruments in oncological physiotherapy, integrating psychometric and clinimetric evidence with clinical applicability to support measurement-based care. METHODS Methods: A multiphase, sequential mixed-methods design will be used. First, a systematic review will be conducted following PRISMA guidelines to identify assessment instruments relevant to oncological physiotherapy with methodological quality, measurement properties, and level of evidence appraised using COSMIN standards. Eligible instruments include patient-reported, clinician-reported, and performance-based outcome measures. This review protocol was previously registered in PROSPERO (CRD42024520846). Second, a three-round electronic Delphi (e-Delphi) process will be conducted via a secure REDCap platform. A multidisciplinary expert panel will evaluate instruments on the basis of an integrated assessment of methodological quality, level of evidence, clinical relevance, and feasibility. Instruments will be organized into eight predefined domains. Structured feedback (median, interquartile range, and percentage agreement) will be provided between rounds. Consensus will be defined a priori as ≥75% agreement. RESULTS Expected results: Preparatory work, including framework development, has been ongoing since late 2024. The systematic review phase began at the end of 2025 and is currently ongoing, with completion expected in 2026. The Delphi consensus process will follow, with the final results anticipated by the beginning of 2027. CONCLUSIONS Conclusions: The IN-GUIDE framework is expected to support standardized, feasible, and clinically applicable assessments in oncological physiotherapy, facilitating measurement-based care, improving clinical decision-making, and promoting integration across multidisciplinary cancer care. CLINICALTRIAL PROSPERO CRD42024520846; https://www.crd.york.ac.uk/PROSPERO/view/CRD42024520846