Medicinal plants have been widely used for medicinal purposes in the treatment of various ailments including human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS). This study evaluated the effect of aqueous extracts of polyherbal formulation (PHF) on peripheral blood mononuclear cells (PBMCs) of an HIV+ patient. In this study, 4 ml of blood was collected from HIV+ patient who has not commenced antiretroviral treatment. PBMCs were isolated using the Ficoll-Paque method and counted using the trypan blue assay. The isolated PBMCs were treated with different concentrations of the PHF (25 50, 100, and 200 μg/ml). Cytotoxicity and proliferation were determined using the WST-8 assay. The percentage viability in this study was 96.74%, whereas the non-viable cell percentage was 3.26%. The lowest percentage of cytotoxicity for the PHF was 0.05% at 25 µg/ml of the extract, while the highest was 5.35% at 200 µg/ml. The mean absorbance scores of the formulation's various concentrations and the control group did not significantly differ from one another (F=0.622, df = 5, p=0.69). There was significant difference (t= -4.887, df =6, 95% CI= -0.1566 to -0.0521, p = 0.003) in mean absorbance scores between control and treatment. The polyherbal formulation exerts the lowest cytotoxicity of 0.05% and significant proliferation on the PBMCs at 25 µg/ml. The PHF has potential immunoproliferative activity with a good safety margin. An in-depth study of the bioactivity of the PHF on individual immune cells is recommended.