Background: It remains unclear whether P2Y 12 inhibitor monotherapy preserves ischemic protection while limiting bleeding risk compared with dual antiplatelet therapy (DAPT) after complex percutaneous coronary intervention (PCI)., Objectives: We sought to assess the effects of P2Y 12 inhibitor monotherapy after 1-month to 3-month DAPT vs standard DAPT in relation to PCI complexity., Methods: We pooled patient-level data from randomized controlled trials comparing P2Y 12 inhibitor monotherapy and standard DAPT on centrally adjudicated outcomes after coronary revascularization. Complex PCI was defined as any of 6 criteria: 3 vessels treated, ≥3 stents implanted, ≥3 lesions treated, bifurcation with 2 stents implanted, total stent length >60 mm, or chronic total occlusion. The primary efficacy endpoint was all-cause mortality, myocardial infarction, and stroke. The key safety endpoint was Bleeding Academic Research Consortium (BARC) 3 or 5 bleeding., Results: Of 22,941 patients undergoing PCI from 5 trials, 4,685 (20.4%) with complex PCI had higher rates of ischemic events. The primary efficacy endpoint was similar between P2Y 12 inhibitor monotherapy and DAPT among patients with complex PCI (HR: 0.87; 95% CI: 0.64-1.19) and noncomplex PCI (HR: 0.91; 95% CI: 0.76-1.09; P interaction = 0.770). The treatment effect was consistent across all the components of the complex PCI definition. Compared with DAPT, P2Y 12 inhibitor monotherapy consistently reduced BARC 3 or 5 bleeding in complex PCI (HR: 0.51; 95% CI: 0.31-0.84) and noncomplex PCI patients (HR: 0.49; 95% CI: 0.37-0.64; P interaction = 0.920)., Conclusions: P2Y 12 inhibitor monotherapy after 1-month to 3-month DAPT was associated with similar rates of fatal and ischemic events and lower risk of major bleeding compared with standard DAPT, irrespective of PCI complexity. (PROSPERO [P2Y12 Inhibitor Monotherapy Versus Standard Dual Antiplatelet Therapy After Coronary Revascularization: Individual Patient Data Meta-Analysis of Randomized Trials]; CRD42020176853)., Competing Interests: Funding Support and Author Disclosures This study was funded by institutional support of the Cardiocentro Ticino Institute, Ente Ospedaliero Cantonale, which had no role in the data analysis, interpretation, or writing of the report. Dr Mehran has received grants from Abbott Laboratories, AstraZeneca, Bayer, Beth Israel Deaconess, BMS, CSL Behring, DSI, Medtronic, Novartis Pharmaceuticals, and OrbusNeich; has received personal fees from Abbott Laboratories, Boston Scientific, Medscape/WebMD, Siemens Medical Solutions, PLx Opco Inc/dba PLx Pharma Inc, Roivant Sciences, Sanofi, and Medtelligence (Janssen Scientific Affairs); has other financial relationships with Abbott Laboratories, Abiomed, The Medicines Company, Spectranetics/Philips/Volcano Corp, and Watermark Research Partners, outside the submitted work; has received nonfinancial support from Regeneron Pharmaceuticals; and has other relationships with Regeneron Pharmaceuticals and Bristol Myers Squibb. Drs Branca and Heg are affiliated with CTU Bern, University of Bern, which has a staff policy of not accepting honoraria or consultancy fees. However, CTU Bern is involved in design, conduct, or analysis of clinical studies funded by not-for-profit and for-profit organizations such as pharmaceutical and medical device companies provide direct funding to some of these studies. Dr Kimura has received research grants from Abbott Vascular, outside the submitted work. Dr Hahn has received grants or contracts from Korean Society of Interventional Cardiology, Abbott Vascular, Biotronik, and Boston Scientific, outside the submitted work. Dr Windecker has received research, travel, or educational grants to the institution from Abbott, Abiomed, Amgen, AstraZeneca, Bayer, Biotronik, Boehringer Ingelheim, Boston Scientific, Bristol Myers Squibb, Cardinal Health, CardioValve, Corflow Therapeutics, CSL Behring, Daiichi-Sankyo, Edwards Lifesciences, Guerbet, InfraRedx, Janssen-Cilag, Johnson & Johnson, Medicure, Medtronic, Merck Sharp & Dohm, Miracor Medical, Novartis, Novo Nordisk, Organon, OrPha Suisse, Pfizer, Polares, Regeneron, Sanofi, Servier, Sinomed, Terumo, Vifor, and V-Wave; serves as unpaid advisory board member and/or unpaid member of the steering/executive group of trials funded by Abbott, Abiomed, Amgen, AstraZeneca, Bayer, Boston Scientific, Biotronik, Bristol Myers Squibb, Edwards Lifesciences, Janssen, MedAlliance, Medtronic, Novartis, Polares, Recardio, Sinomed, Terumo, V-Wave and Xeltis; and is a member of the steering/executive committee group of several investigator-initiated trials that receive funding by industry without impact on his personal remuneration. Dr Gibson has received research or grant funding from CSL Behring, Janssen Pharmaceuticals, Johnson & Johnson Corporation, and SCAD Alliance; has received consulting fees from Amarin, Amag Pharmaceuticals, Angel Medical Corporation, Anthos Therapeutics, AstraZenca, Bayer Corporation Bioclinica, Boston Clinical Research Institute, Boston Scientific, Bristol Myers Squibb, Caladrius Biosciences, Cardiovascular Clinical Science Foundation, Cardiovascular Research Foundation, CeleCor Therapeutics, CSL Behring, CytoSorbents Medical, Inc, Duke Clinical Research Institute, Eidos Therapeutics, EXCITE International, Gilead Sciences, Inc., Inari, Janssen Pharmaceuticals Johnson & Johnson Corporation, MD Magazine, MedImmune, Medtelligence, MedTrace, Merck Microport, Micodrop, LLC, Novo Nordisk, Paratek, PERT Consortium, Pfizer, PhaseBio, PHRI, PLxPharma, Revance Therapeutics, SCAI, Smart Medics, Somahlution, and Web MD; and has received personal fees from UpToDate in Cardiovascular Medicine, and other from Absolutys, nference, and Dyad Medical, outside the submitted work. Dr Watanabe has received honoraria for lectures from Abbott Medical Japan, Daiichi-Sankyo, Pfizer, and Kowa, outside the submitted work. Dr Zhu has received grants from AstraZeneca and Chugaipharma; and has received personal fees from AstraZeneca, Novartis, Sanofi, Medtronic, and Chugaipharma, outside the submitted work; and has received nonfinancial support from Medtronic. Dr Vranckx has received consulting fees or honoraria from Bayer AG, Daiichi-Sankyo, Servier, Bristol Myers Squibb-Pfizer, Menarini, and CSL Behring; has participated data safety monitoring or advisory boards for Novartis; and his institution has received research grants from Daiichi-Sankyo and Medtronic. Dr Serruys has received personal fees from SMT, Philips, Xeltis, Novartis, and Merillife, outside the submitted work. Dr Dangas has received grants from AstraZeneca, during the conduct of the study, Abbott Vascular, Boston Scientific, Medtronic, Daiichi-Sankyo, and Bayer, outside the submitted work; and has received personal fees from Biosensors and Boston Scientific. Dr McFadden has received personal fees from Cardialysis BV, Rotterdam, the Netherlands, outside the submitted work. Dr Angiolillo has received consulting fees or honoraria from Abbott, Amgen, AstraZeneca, Bayer, Biosensors, Boehringer Ingelheim, Bristol Myers Squibb, Chiesi, Daiichi-Sankyo, Eli Lilly, Haemonetics, Janssen, Merck, PhaseBio, PLx Pharma, Pfizer, and Sanofi; and his institution has received research grants from Amgen, AstraZeneca, Bayer, Biosensors, CeloNova, CSL Behring, Daiichi-Sankyo, Eisai, Eli Lilly, Gilead, Janssen, Matsutani Chemical Industry Co, Merck, Novartis, Osprey Medical, Renal Guard Solutions, and Scott R. MacKenzie Foundation, outside the submitted work. Dr Valgimigli has received grants from Terumo; and has received personal fees from AstraZeneca, Terumo, Alvimedica/CID, Abbott Vascular, Daiichi-Sankyo, Bayer, CoreFlow, Idorsia Pharmaceuticals LTD, Universität Basel, Department. Klinische Forschung, Bristol Myers Squibb SA, Medscape, Biotronik, and Novartis, outside the submitted work. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)