OBJECTIVE To investigate the relationship between serum free fatty acids (FFAs) levels and the severity of coronary artery lesions in elderly patients with coronary heart disease (CAD). METHODS A total of 172 elderly patients who underwent coronary angiography were divided into CAD group (n = 128) and non-CAD group (n = 44) according to the results of coronary angiography. Serum FFAs and lipid levels were measured and the Gensini score were calculated. RESULTS No matter the differences between age, gender and the usage of statins or not, there was no statistical significance in FFAs levels (P > 0.05). In terms of the Gensini score, it was higher in patients aged 70-79 years than in patients 60-69 years old [15.00 (5.00, 34.00) vs. 10.00 (2.00, 24.00), P < 0.05], higher in men than women [14.00 (4.00, 34.00) vs. 7.00 (2.50, 19.75), P < 0.05], and higher in patients on statins [13.50 (4.25, 33.50) vs. 6.50 (2.00, 18.00), P < 0.05]. The serum FFAs levels [449.50 (299.00, 624.75) mEq/L vs. 388.00 (258.50, 495.25) mEq/L, P < 0.05] and Gensini score [17.50 (8.00, 41.75) vs. 1.00 (0, 5.00), P < 0.05] were higher in the CAD group than in the non-CAD group. In the CAD group, there was no statistical significance in FFAs levels among patients with different numbers of diseased coronary vessels (P > 0.05). Furthermore, the FFAs levels were positively correlated with the Gensini score (r = 0.394, P = 0.005). Regression analysis showed that the FFAs levels were related to the Gensini score independently after adjusting for the other risk factors. CONCLUSIONS The serum FFAs levels were associated with the Gensini score in elderly patients with CAD. It might indicate FFAs as a biomarker predicting the severity of coronary artery lesions.