Background/Objectives: T. pallidum subsp. pallidum is a spirochete that only causes disease in humans as the causative agent of syphilis. HIV and syphilis have common transmission routes. In the present study, our aim was to evaluate the presence of syphilis coinfection in people living with HIV using conventional and reverse algorithms and to investigate its effects on laboratory parameters. Methods: The traditional algorithm for syphilis begins testing with the non-treponemal test. If the non-treponemal test is reactive, a treponemal test is then used to confirm syphilis infection. The reverse algorithm for syphilis begins testing with the treponemal test. If this test is reactive, then a non-treponemal test is performed. When the non-treponemal test is non-reactive, a second treponemal test is performed. Results: A total of 200 patients were included in the study. While 22 patients were determined to be syphilis-positive using the traditional algorithm, 37 patients were determined to be syphilis-positive using the reverse algorithm. Most of the patients who had syphilis coinfection were homosexual. Conclusions: It was found that syphilis coinfection had no effects on CD4+ T-lymphocyte and CD8+ T-lymphocyte values, CD4/CD8 rates, and HIV RNA amounts. People living with HIV must be screened and followed up for syphilis and other sexually transmitted diseases at certain intervals.