The immune system may play important roles in the pathogenesis of cardiovascular disease. T-cell mediated immune responses in human progression of atherosclerotic disease and hypertension have recently been revealed, but the significance of T-cell specific chemokines in coronary artery heart disease has not been confirmed. In our study, we sought to examine the association between serum levels of the monokine induced by gamma interferon (MIG)/CXCL9 and the severity of coronary artery disease. We studied 117 patients with coronary heart disease and 80 patients with no coronary heart disease. The severity of coronary artery disease was assessed via coronary artery angiography and the Gensini score was calculated. Clinical and biochemical indices, including serum levels of MIG, CD40L, and IFN-γ were analyzed in all subjects. Finally, we found there was a significant correlation between serum MIG levels and the severity of coronary artery disease, quantified by the Gensini score (r = 0.122, P = 0.009). Furthermore, multivariate regression analysis revealed that serum MIG levels were independently associated with the severity of coronary artery disease, quantified by the Gensini score (β = 0.100, P = 0.021). Our findings could indicate the potential clinical implication of MIG with respect to early coronary artery atherosclerosis in humans.