Background and Objectives: Preterm delivery is an important subject in gynecology, obstetrics and pediatrics. It is defined as regular uterine contractions every five to eight minutes or less, lasting for 30 seconds. It is associated with progressive changes in the cervix, resulting in delivery after 22 weeks and before 37 weeks of gestation. This study aimed to evaluate the role of Chlamydia trachomatis infection in women with preterm delivery. Materials and Methods: This case-control study was performed on 75 women with preterm delivery (case group) and 75 women with term delivery (control group). The research tools included a questionnaire, polymerase chain reaction (PCR) assay of cervical swab samples and ELISA assay of umbilical cord blood samples. Fisher’s exact test and t test were also performed to compare qualitative variables between the two groups. Results: In this study, the mean age of subjects was 26.55 ± 0.53 years in the control group and 26.76 ± 0.56 years in the case group. The prevalence of C. trachomatis in the cervical swab samples was 7 (9.33%) in the control group and 2 (2.67%) in the case group. There was no C. trachomatis IgM antibody in either of the groups, while there was 1 (1.33%) C. trachomatis IgG antibody in both groups. Conclusion: The results of the present study showed that there was no significant relationship between C. trachomatis infection and preterm delivery.