Abstract Background Statins are used for coronary artery disease (CAD) primary and secondary prevention. Limited studies on the association of statin use before acute coronary syndrome (ACS) with clinical presentation and outcomes are available. Purpose We compared statin-user and statin-naïve ACS patients for clinical and angiographic findings and in-hospital and 3-year outcomes following percutaneous coronary intervention (PCI). Methods Successive patients with ACS who underwent PCI from Sep’17 to Dec’23 were enrolled in the ACC-NCDR-CathPCI registry in India. Details of risk factors, clinical presentation, coronary angiography, interventions and in-hospital were recorded. Follow-up data in a sub-cohort recruited from Apr’19 to Mar’22 were obtained for incident major cardiovascular events (MCE) (cardiovascular deaths, recurrent ACS, PCI and bypass surgery). Results 8296 ACS patients were enrolled; prior statin use was in 3149 (38%) and statin naïve were 5147 (62%). Statin-user vs statin-naïve patients were older (61.6+10 vs 59.7+11y), with more hypertension (60.1 vs 48.6%), diabetes (35.8 vs 31.8%), pre-existing CAD (PCI 20.9 vs 9.1%; CABG 5.0 vs 2.3%) and lower mean total, LDL, and NHDL cholesterol (p<0.001). Statin users had less ST-elevation myocardial infarction (STEMI) (28.4% vs 45.2%), more non-STEMI (65.2 vs 50.8%), better LVEF (46.3+10 vs 44.5+10%), >2 coronary stents (35.5 vs 29.5%), lower mechanical circulatory support (2.2 vs 3.9%) and lower median hospitalization (66.1 vs 68.5h) (p<0.001). In statin-users incidence of in-hospital CAD deaths was 29 (0.92%) vs 78 (1.52%) (odds ratio, OR 0.61, 95% confidence intervals 0.39-0.93) and all-cause deaths 33 (1.05) vs 91(1.77%) (OR 0.59, 95%CI 0.39-0.88) (p<0.01). ORs attenuated following multivariate adjustments for risk factors, clinical presentation and interventions. In the follow up cohort (n=3813, high-intensity statins 99.6%), among baseline statin-users incident MCE was 98 (6.9%) vs 214 (8.9%) (hazard ratio, HR 0.76, 95%CI 0.59-0.97) and CVD deaths were in 46 (3.2%) vs 113 (4.7%) (HR 0.68, 95%CI 0.48-0.96) with attenuation following adjustment for baseline clinical variables and interventions. Conclusions Acute coronary syndrome patients taking pre-admission statins have significantly lower in-hospital and long-term cardiovascular and all-cause mortality following PCI.