Background The number of HIV/AIDS cases in Turkey is increasing rapidly, as is the number of cases worldwide. The aim of this study is to evaluate the characteristics of the clinical and laboratory findings and epidemiological features of HIV/AIDS patients to obtain useful data on the epidemic type and transmission routes associated with Turkey and to identify risk factors for mortality. Methods The patient records of 144 HIV-infected patients who were admitted to our clinic between 2000 and 2015 were analyzed retrospectively. Results Most of the cases (55%) were diagnosed due to the detection of anti-HIV-positive individuals without clinical symptoms. The mean CD4 + lymphocyte count on first admission was 108 cells/μL for those admitted before 2009 and 265 cells/μL for those admitted after 2009 (p = 0.003). When the pre- and post-2009 groups were compared for the status of the disease, 55.6 and 44.4% of patients were in the AIDS stage, respectively (p = 0.04). The most noted opportunistic infection was mycobacterial, and throughout the follow-up, 31.2% of the cases were fatal. Conclusions Early diagnosis of HIV infection can have a direct impact on prognosis and survival. Therefore, screening laboratory investigations should be extended, particularly in high-risk groups.