The endometrium produces MUCIN-1 (MUC-1) and cyclooxygenase-2 (COX-2), which are essential for implantation. MUC-1 is required for adhesion, while COX-2 is necessary for decidualization. Variations or polymorphisms in MUC-1 and COX-2 can lead to changes in endometrial receptivity. This study investigated the relationship between MUC-1 and COX-2 polymorphisms and endometrial receptivity in endometriosis patients. Blood DNA samples were collected from 35 patients with endometriosis and 32 healthy patients between days 19 to 24 of their menstrual cycle (secretory phase). MUC-1 polymorphism was determined using the Amplification Refractory Mutation System (ARMS), and COX-2 gene polymorphism was assessed using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). The frequency distribution of gene polymorphisms between the two groups was compared using bivariate analysis. There were seven genotypic combinations of MUC-1 and COX-2: AAGC; AAGG; GACC; GAGC; GAGG; GGGC; GGGG. The AAGC genotype combination test was significant, with an OR=6.43 (95% CI:1.09–7.62) and p=0.01. In conclusion, combining MUC-1 and COX-2 (AAGC) genotypes results in endometrial receptivity defects in endometriosis.