We aimed to investigate the relationship between platelet-to-lymphocyte ratio (PLR) and contrast-induced acute kidney injury (CI-AKI) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI). A total of 2563 patients diagnosed with STEMI and underwent primary pPCI were retrospectively included in the study. Levels of PLR and creatinine were measured before and at 72 hours after pPCI. Patients were divided into 2 groups: non-CI-AKI group and CI-AKI group. Contrast-induced acute kidney injury occurred in 6.4% of the overall study population. Patients in the CI-AKI group had significantly higher PLR than those in the non-CI-AKI group (169.18 ± 81.01 vs 149.49 ± 74.54, P < .001). In logistic regression analysis, PLR was an independent predictor of CI-AKI (odds ratio [OR]: 1.774, 95% CI: 1.243-2.532, P = .002), along with age, use of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker prior to the procedure, preprocedural creatinine level, amount of contrast material used during the procedure, and hypertension. Increased PLR levels are independently associated with a greater risk of CI-AKI in patients undergoing primary PCI for STEMI.