Chlamydia trachomatis is the most common cause of sexually transmitted diseases that is not of viral origin and there is accumulating evidence of a significant role played by this pathogen in causing male factor infertility. This study thus aimed to determine the prevalence of C. trachomatis among infertile males and to evaluate their association with fertility status and abnormal semen characteristics. This study included 215 infertile male subjects who visited a major fertility clinic in Warri, Delta state, Nigeria. Forty apparently healthy males without complaints of infertility were enrolled as controls. Blood samples were collected from patients aseptically using venous puncture and semen samples were obtained after masturbation. C. trachomatis IgG antibodies were assayed for in blood specimens using the Dot rapid Assay Kit flow through Ct cassette and positive samples were further screened with an enzyme immunoassay technique. Semen samples were analyzed following World Health Organization guidelines. Forty-two (19.5%) out of 215 infertile male subjects were found sero-positive for C. trachomatis. C. trachomatis was significantly associated with male infertility when compared to controls (P<0.001). Age groups 20-29 years (43.3%) and 30-39 years (22.1%) significantly had higher prevalence of C. trachomatis (P<0.001), as compared to age groups 40-49 (7.9%) and > 50 years (3.7%). Sero-positivity for C. trachomatis antibodies was significantly associated with oligozoospermia (22.5%) and azospermia (61.5%) than with teratozoospermia (7.3%) and asthenozoospermia (6.3%) (P<0.001). The prevalence of C. trachomatis among infertile males was high; there was an association between C. trachomatis infection and poor semen characteristics and infertility. There is need for routine screening for the pathogen in males with complaints of infertility so as to rule out this potentially correctable/reversible cause of infertility.____________________________________________________________________________________