Background Glycoprotein IIb/IIIa inhibitors (GPIs) in combination with clopidogrel improve clinical outcome in ST-elevation myocardial infarction (STEMI); however, finding a balance that minimizes both thrombotic and bleeding risk remains fundamental. The efficacy and safety of GPI in addition to ticagrelor, a more potent P2Y12-inhibitor, have not been fully investigated. Methods 1,630 STEMI patients who underwent primary percutaneous coronary intervention (PCI) were analyzed in this subanalysis of the ATLANTIC trial. Patients were divided in three groups: no GPI, GPI administration routinely before primary PCI, and GPI administration in bailout situations. The primary efficacy outcome was a composite of death, myocardial infarction, urgent target revascularization, and definite stent thrombosis at 30 days. The safety outcome was non-coronary artery bypass graft (CABG)-related PLATO major bleeding at 30 days. Results Compared with no GPI ( n = 930), routine GPI ( n = 525) or bailout GPI ( n = 175) was not associated with an improved primary efficacy outcome (4.2% no GPI vs. 4.0% routine GPI vs. 6.9% bailout GPI; p = 0.58). After multivariate analysis, the use of GPI in bailout situations was associated with a higher incidence of non-CABG-related bleeding compared with no GPI (odds ratio [OR] 2.96, 95% confidence interval [CI] 1.32-6.64; p = 0.03). However, routine GPI use compared with no GPI was not associated with a significant increase in bleeding (OR 1.78, 95% CI 0.88-3.61; p = 0.92). Conclusion Use of GPIs in addition to ticagrelor in STEMI patients was not associated with an improvement in 30-day ischemic outcome. A significant increase in 30-day non-CABG-related PLATO major bleeding was seen in patients who received GPIs in a bailout situation.