In the low-income HIV-endemic regions of sub-Saharan Africa, malignancies related to HIV have long been recognized as a major public health problem. However, epithelial malignancies associated with older age, such as breast cancer, are also rising dramatically in those regions. We compared consecutive HIV-positive and -negative black women diagnosed with breast cancer at a large public hospital in Soweto, South Africa, on age, year of diagnosis, stage, grade, and receptor status, and grouped HIV-positive patients by CD4 cell counts. We computed prevalence ratios of the associations of HIV status and CD4 category with stage, grade, receptor status, and among the HIV-positive patients, receipt of ART, controlling for age and year of diagnosis. Of 1,092 patients, 765 were tested for HIV; 151 (19.7 %) tested positive, a prevalence similar to that in the source population. Although, HIV-positive patients were younger than HIV-negative patients (p < 0.001), HIV status was not associated with the tumor characteristics. Thirty-seven women (25.9 %) had CD4 cell counts <200 cells/μl. Patients in that severely immunocompromised group were older than those in the other groups (p = 0.01). This study is the first to analyze the association of HIV with breast cancer in a large sample. Based on similar HIV prevalence in our sample and the population of the hospital's catchment area, clinicians serving HIV-endemic communities should promote routine HIV testing of younger breast cancer patients and immediate treatment of those who test positive, prior to the initiation of chemotherapy. Research is needed on treatment and outcomes given HIV and low CD4 cell count.