Secretory phospholipasesA(2) (sPLA(2)s) form a large family of structurally related enzymes widespread in nature. Herein, we studied the inhibitory effects of sPLA(2)s from Vipera lebetina (VLPLA(2)), Vipera berus berus (VBBPLA(2)), and Naja naja oxiana (NNOPLA(2)) venoms on (i) human platelets, (ii) four different bacterial strains (gram-negative Escherichia coli and Vibrio fischeri; gram-positive Staphylococcus aureus and Bacillus subtilis) and (iii) five types of cancer cells (PC-3, LNCaP, MCF-7, K-562 and B16-F10) in vitro. sPLA(2)s inhibited collagen-induced platelet aggregation: VBBPLA(2) IC(50) = 0.054, VLPLA(2) IC(50) = 0.072, NNOPLA(2) IC(50) = 0.814 μM. p-Bromophenacylbromide-inhibited sPLA(2) had no inhibitory action on platelets. 36.17 μM VBBPLA(2 )completely inhibited the growth of gram-positive Bacillus subtilis whereas no growth inhibition was observed towards gram-negative Escherichia coli. The inhibitory action of sPLA(2)s (~0.7 μM and ~7 μM) towards cancer cells depended on both venom and cell type. VBBPLA(2 )(7.2 μM) inhibited significantly the viability of K-562 cells and the cell death appeared apoptotic. The sPLA(2)s exhibited no inhibitory effect towards LNCaP cells and some effect (8%-20%) towards other cells. Thus, already sub-μM concentrations of sPLA(2)s inhibited collagen-induced platelet aggregation and from the current suite of studied svPLA(2)s and test cells, VBBPLA(2) was the most growth inhibitory towards Bacillus subtilis and K-562 cells.