Protein Z (PZ) is the cofactor of PZ dependent inhibitor (ZPI) that inhibits activated coagulation factor X. PZ was expected to play a role in coronary artery disease (CAD) but with inconsistent clinical findings. We therefore evaluated whether PZ plasma level and/or three genetic variants encoding for low PZ plasma level were associated with premature CAD in stable young post-myocardial infarction (MI) patients. PZ plasma level and three polymorphisms A-13G, G-103A and G79A were determined in 176 young stable post-MI patients and in 176 sex- and age-matched controls (FITE-NAT population). Moreover the genotypes, resulting from the combination of the three polymorphisms (A-13G/G-103A/G79A), were studied. PZ plasma level and the number of patients disclosing a PZ deficiency did not differ between post-MI patients and controls. The presence of the mutated allele for each polymorphism was associated with a significantly reduced level of PZ. The A-13G polymorphism was associated with premature CAD only in univariate analysis. Whereas, the presence of rare genotypes of PZ gene was an independent risk factor for premature CAD. In conclusion, PZ plasma level is not a key player in the pathophysiology of premature coronary artery disease. But, rare genotypes of PZ gene were found to be associated with premature CAD.