Background The therapeutic effectiveness of mesenchymal stem cells (MSCs) and their secretome can be enhanced by means of physical, chemical and biological preconditioning. Arsenicum album 30C (AA30) has been one of the leading homeopathic medicines used in prophylaxis against SARS-CoV-2 infection. Aims This study aimed to investigate whether AA30 preconditioning could influence the growth factors and cytokine profile of the human dental pulp-derived MSC (DPD-MSC) secretome. Also, to test the efficacy of the AA30-preconditioned DPD-MSC secretome in ameliorating the lipopolysaccharide (LPS)-induced cytokine storm in human peripheral blood mononuclear cells (PBMCs) as an in-vitro cellular model. Methods The cytotoxicity of AA30 was assessed in DPD-MSCs by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Growth factors and cytokine levels in the AA30-preconditioned DPD-MSC secretome were analysed by fluorescence-activated cell sorting (FACS) analysis. The angiogenic potential of the AA30-preconditioned DPD-MSC secretome was assessed by chick yolk-sac membrane (YSM) assay. Culture medium with 0.001% ethanol was used as vehicle control. The efficacy of the AA30-preconditioned DPD-MSC secretome in ameliorating the cytokine storm was assessed in LPS pre-treated PBMCs. The mRNA and protein expression of inflammatory markers such as IL-1β, IL-6 and IL-10 were analysed by using RT-PCR and FACS analysis respectively. Results AA30 did not exhibit cytotoxicity in the concentration range of 1% to 50%. Furthermore, the AA30-preconditioned DPD-MSC secretome exhibited a significant increase in the levels of angiogenic factors, such as human angiopoietin-2, EPO and PDGF-AA, and decreased levels of cytokines, such as TNF-α, CXCL-8 and IL-6. The AA30-preconditioned DPD-MSC secretome showed augmented angiogenesis compared to vehicle controls. The DPD-MSC secretome ameliorated LPS-induced mRNA and protein expression of IL-1β, IL-6 and IL-10 in PBMCs. Conclusion The AA30-preconditioned DPD-MSC secretome augmented angiogenesis and ameliorated the LPS-induced cytokine storm in human PBMCs in vitro. Our data demonstrate that AA30 preconditioning enhances the therapeutic potency of MSCs and their secretome.