Background: Neutrophil gelatinase-associated lipocalin (NGAL) is an early marker of renal tubular damage. We investigated the incidence and possible implications of elevated NGAL levels (suggesting renal damage) compared to both functional and damage markers (manifested as serum creatinine [sCr] elevation) and no NGAL/sCr change, among ST-elevation myocardial infarction (STEMI) patients treated with primary percutaneous coronary intervention (PCI). Methods: We included 131 patients with STEMI treated with PCI. Blood samples for plasma NGAL were drawn 24 h following PCI. We used the terms NGAL(–) or NGAL(+) with levels ≥100 ng/mL suggesting renal tubular damage and the terms. sCr(–) or sCr(+) to consensus diagnostic increases in sCr defining acute kidney injury. Patients were also assessed for in hospital-adverse outcomes. Results: Of the study patients, 56 (42%) were NGAL(–)/sCr(–), 58 (44%) NGAL(+)/sCr(–), and 18 (14%) were both NGAL(+)/sCr(+). According to the 3 study groups, there was a stepwise increase in the proportion of left ventricular ejection fraction ≤45% (43 vs. 60. vs. 72%; p = 0.04), in-hospital adverse outcomes (9 vs. 14 vs. 56%; p < 0.001) and their combination. Specifically, more NGAL(+)/sCr(–) patients developed the composite endpoint when compared to NGAL(–)/sCr(–) patients (64 vs. 46%; OR 2.1, [95% CI 1.1–4.5], p = 0.05). A similar and consistent increase was observed in peak sCr, length of hospital stay, and C-reactive protein levels. Conclusions: Elevated NGAL levels suggesting renal tubular damage, increased inflammation, or both are common among STEMI patients and are associated with adverse outcomes even in the absence of diagnostic increase in sCr.