Background Chlamydia trachomatis infection is common and largely asymptomatic in women. If untreated, it can lead to sequelae such as pelvic inflammatory disease and infertility. It is unknown whether a patient's self-reported history of Chlamydia trachomatis infection is a valid marker of past infection. Objective Our objective was to evaluate the validity of women's self-reported history of Chlamydia trachomatis infection compared with Chlamydia trachomatis serology, a marker for previous infection. Study Design We analyzed data from the Fertility After Contraception Termination study. We compared participants’ survey responses with the question, “Have you ever been told by a health care provider that you had Chlamydia?” to serological test results indicating the presence or absence of antibodies to Chlamydia trachomatis as assessed by a microimmunofluorescence assay. Prevalence of past infection, sensitivity, specificity, predictive values, and likelihood ratios were calculated. The Cohen's kappa statistic was computed to assess agreement between self-report and serology. Results Among 409 participants, 108 (26%) reported having a history of Chlamydia trachomatis infection, whereas 146 (36%) had positive serological test results. Relative to positive microimmunofluorescence assay, the sensitivity and specificity of self-reported history of Chlamydia trachomatis infection were 52.1% (95% confidence interval, 43.6–60.4%) and 87.8% (95% confidence interval, 83.3–91.5%), respectively. The positive predictive value of the self-report was 70.4% (95% confidence interval, 60.8–78.8%), and the negative predictive value was 76.7% (95% confidence interval, 71.6–81.4%). The likelihood ratio was found to be 4.28. Agreement between self-report and serology was found to be moderate (kappa = 0.42, P <.001). Conclusion Self-reported history of Chlamydia trachomatis infection commonly yields false-negative and false-positive results. When definitive status of past Chlamydia trachomatis infection is needed, serology should be obtained.