Intracranial multimodal monitoring (iMMM) is increasingly used in neurocritical care, but a lack of standardization hinders its evidence-based development. Here, we devised core outcome sets (COS) and reporting guidelines to harmonize iMMM practices and research.An open, decentralized, three-round Delphi consensus study involved experts between December 2023 and June 2024. Items-spanning three domains: (i) patient characteristics, (ii) practices, and (iii) outcomes-with ≥ 75% agreement were classified as strong agreement, while those with 50-75% were reconsidered in subsequent rounds, requiring ≥ 66% for moderate agreement.An international, multidisciplinary panel comprised 58 neurocritical physicians and researchers with low attrition (12%). They were predominantly from Western regions (96%), actively involved in iMMM (82%), at least weekly (72.4%), with more than 10 years of specific experience (57%). Of the 127 items assessed for inclusion in COS and reporting guidelines, 45 (35.4%) reached strong and 8 (6.3%) moderate agreement. Main strong agreement items were: (i) demographics: age (98%) and sex/gender (90%); comorbidities: coagulation/platelet disorders (95%); initial scoring: Glasgow Coma Scale (97%) and pathology-specific scores (90%); active treatments: antithrombotics (95%) (ii) clinical practice: iMMM implantation indications (98%) and iMMM-guided interventions (91%); surgical practice: targeting strategies (97%) and concomitant external ventricular drainage (97%); technical details: recording modalities (98%); (iii) monitoring parameters: duration (97%) and triggered interventions (95%); standardized outcome reporting (93%); surgical complications (e.g., postoperative intracranial hemorrhages, CNS infections, and probe misplacement, all > 90%) and adverse events (accidental dislodgement, probe breakage, and technical malfunctions, all > 90%).This consensus establishes foundational COS and reporting guidelines for iMMM in neurocritical care. These harmonization tools can enhance research quality, comparability, and reproducibility, facilitating evidence-based practices for this emerging technology. However, challenges remain in developing purpose-specific guidelines and adapting them to diverse clinical and research settings.