Untreated tropical parasitic co-infections appear to speed the progression of HIV-1 disease. However, to date, there have been few studies conducted in resource limited settings to ascertain the interaction of parasitic co-infection where HIV/AIDS management largely depends on CD4+ T lymphocyte cells counts and WHO clinical staging. This study aimed to determine the prevalence of parasites, their association with CD4+ T lymphocyte cells changes and clinical manifestation of HIV-infection in patients attending HIV/AIDS management clinics in Tanzania. Adult HIV-infected patients registering for the first time at HIV/AIDS management clinics were recruited; with physical examination and laboratory tests performed at baseline and after 6 months. Patients were assigned a clinical stage and screened for helminths and Plasmodium sp . co-infection, CD4+ T lymphocyte cells, haemoglobin and HIV-1 p24 antigen. Of the 421 HIV-1 infected patients studied, 198 (47.0%) were co-infected with one or more parasites. Of those studied, 93/421(22.1%) had helminth only co-infection, and 50/421(12.9%) had Plasmodium sp only co-infection. Mixed Plasmodium sp and helminth co-infection was diagnosed in 55/421(13.0%) patients. Helminths frequently diagnosed included: hookworm 65/421(15.4%), Schistosomiasis 49/421(11.6%), Strongyloides stercoralis 57/421(13.5%), and Ascaris lumbricoides 54/421(12.8%). No statistical association was found between CD4+ T lymphocyte cells <200/µl, or WHO clinical stage III/IV with parasite co-infections (AOR 1.2, 95%CI 0.8-1.8). Anaemia was common in parasite co-infected patients (32.8% vs 18.8%). Parasite co-infection was associated with risk of anaemia (AOR 2.1, 95%CI 1.3-3.2). In multivariable logistic regression analysis, baseline CD4+ T lymphocyte cells <200/µl was significantly associated with CD4+ T lymphocyte cells <200/µl (AOR 2.4, 95%CI 1.3-4.7) at six months. HIV-1 P24 antigen mean concentration was higher in parasite co-infected patients (ranges 47.6 to 56.9) as compared to patients without parasite co-infection (5.5). We have looked at one set of parasites and found high prevalence of malaria and helminth co-infection in HIV-infected individuals. Given the available reports on health impacts of helminth co-infection in HIV/AIDS patients and the anecdotal reports of helminth’s health effects in HIV-uninfected persons, helminths and other prevalent parasites should not be ignored in HIV/AIDS programs. Based on local helminth epidemiology and HIV-infected cohort specific helminths co-infection prevalence data, mass treatment of soil transmitted helminths can be incorporated into HIV/AIDS management programmes.