Apoptosis or programmed cell death is an important outcome of cell fate and is influenced by several factors. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a member of the EGF family of growth factors and is synthesized as a membrane-associated precursor molecule (proHB-EGF). Under stressful conditions proHB-EGF is proteolytically cleaved and released as a soluble ligand (sHB-EGF) that activates the EGF receptor. We show that antibody against CD9, a membrane tetraspanin, induces apoptosis in mouse embryonic stem cells through the activation of specific EGF receptor residues (Y-1148 and Y-1173), caspase-3 and MAPK signalling. HB-EGF and the p38 inhibitor PD169316 act in a pro-survival manner by perturbing phosphorylation of EGFR Y-1173, suggesting its importance in inducing apoptosis. Caspase-3 activation was attenuated in the presence of HB-EGF and PD169316. Furthermore, HB-EGF and PD169316 prevent p38 phosphorylation while promoting the phosphorylation of the pro-survival SAPK/JNK and ERK. These results suggest a role for CD9 as an endogenous suppressor of apoptosis, an effect that is mimicked by HB-EGF and PD169316.