Objectives: To estimate the prevalence of infections caused by Neisseria gonorrheae, Chlamydia trachomatis, and Treponema pallidum in the New Caledonian population aged 18 to 49 years and to identify associated sociodemographic factors. Methods: A cross-sectional study using a three-stage stratified proportional cluster random sampling design. The sample was weighted to reflect the study’s target population. Prevalences were adjusted for the age of this population, and risk factors were identified using multivariate logistic regression. Results: Prevalences were 3.5% (95% confidence interval (CI): [1.9–5.1]) for Neisseria gonorrheae, 9% [6.6–11.4] for Chlamydia trachomatis, with 2.1% [0.8–3.3] of co-infections with these two diseases, 0.4% [0.0–0.9] for active syphilis, and 3% [1.7–4.3] for late-stage syphilis. Multivariate models revealed, depending on the infection in question, increased risks associated with age, sex, ethnicity, province of residence, living alone, and having a low level of education. A disparity in the ethnic risk among Melanesians based on place of residence was identified in the occurrence of Chlamydia trachomatis. Conclusion: This first probabilistic survey of the general population establishes significant prevalence rates for these three sexually transmitted infections. It highlights associated sociodemographic factors that will help guide future sexual health prevention policies in New Caledonia. (R.A.)