Background The aim of the study was to investigate the relationship between severity of coronary artery disease ( CAD) assessed with SYNTAX score ( SS) and myocardial performance index ( MPI) in stable CAD. Methods The study participants consisted of 106 consecutive patients (mean age: 57.6 ± 9.5 years) with angiographically proven obstructive stable CAD and 30 patients with nonobstructive CAD (control group) (mean age: 58.0 ± 7.6 years). The MPI was calculated by using pulsed-wave Doppler before coronary angiography. Coronary angiography was performed in all patients. The SS was prospectively calculated in 106 obstructive CAD patients. Patients were partitioned into 3 groups based on SS. Frequencies of risk factors, biochemical and hematological data were recorded in all patients. Results The SS tertiles were defined as SSlow ≤ 8 (n = 35), SSmid ≤ 17 (n = 36), and SShigh > 17 (n = 35). The patients with SShigh group (mean MPI; 0,48 ± 0.06) based on SS had significantly higher MPI values compared with the SSmid (mean MPI; 0,44 ± 0.05), SSlow (mean MPI; 0.43 ± 0.06), and control (mean MPI; 0.41 ± 0.05) groups (P < 0.05 for all). The MPI levels of control group were also lower than compared with SSmid group (P = 0.006). The MPI value was significantly correlated with SS (r = 0.564, P < 0.001), diabetes (r = 0.355, P < 0.001), hypertension (r = 0.326, P < 0.001), and ejection fraction ( EF) (r = −0.224, P = 0.018) in bivariate analysis. Multivariate regression analysis showed that MPI was independently associated with SS (β = 0.486, P < 0.001) and diabetes (β = 0.205, P = 0.028). Conclusion Although the normal EF, MPI value was impaired in proportion to the severity of CAD in patients with stable CAD.