Coronary plaque rupture is associated with a systemic inflammatory response. The relationship between baseline N-terminal pro B-type natriuretic peptide (NT-proBNP), a prognostic marker in patients with acute coronary syndromes, and systemic inflammatory mediators in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI) is not well described. Of 5,745 STEMI patients treated with primary PCI in the APEX-AMI trial, we evaluated the relationship between baseline NT-proBNP levels and baseline levels of inflammatory markers and markers of myonecrosis in a subset of 772 who were enrolled in a biomarker substudy. Spearman correlations (r (s)) were calculated between baseline NT-proBNP levels and a panel of ten systemic inflammatory biomarkers. Interleukin (IL)-6, a pro-inflammatory cytokine, was significantly positively correlated with NT-proBNP (r (s) = 0.317, P < 0.001). In a sensitivity analysis excluding all heart failure patients, the correlation between baseline IL-6 and NT-proBNP remained significant (n = 651, r (s) = 0.296, P < 0.001). A positive association was also observed with high sensitivity C-reactive protein (r (s) = 0.377, P < 0.001) and there was a weak negative correlation with the anti-inflammatory cytokine IL-10 (r (s) = -0.109, P = 0.003). No other significant correlations were observed among the other testes inflammatory cytokines and chemokines. In STEMI patients undergoing primary PCI, the pro-inflammatory cytokine IL-6 was modestly correlated with baseline NT-proBNP levels. This relationship remained significant in patients without heart failure. This finding is consistent with pre-clinical and clinical research suggesting that systemic inflammation may influence NT-proBNP expression independently of myocardial stretch.