During apoptosis, proteolytic cleavage of Bax at the amino-terminus generates a truncated Bax of ~18 kDa (p18Bax) and an amino-terminal peptide of ~3 kDa (p3Bax). While extensive studies have shown that p18Bax behaves like a BH3 protein with enhanced pro-apoptotic function over that of the full-length Bax (p21Bax), little is known about the function of p3Bax in apoptosis. We have previously shown that Bax and Ca²⁺ play a synergistic role in amplifying apoptosis signaling, and that store-operated Ca²⁺ entry (SOCE) contributes to Bax-mediated apoptosis in prostate cancer cells. Here we test if p3Bax can contribute to regulation of Ca²⁺ signaling during apoptosis, through use of a membrane penetrating peptide (TAT) to facilitate delivery of recombinant p3Bax into NRP-154 cells, a prostate epithelial cell line with tumorigenic capacity. We find that TAT-p3Bax fusion peptide can enhance thapsigargin-induced apoptosis in NRP-154 cells, elevate SOCE activity and increase IP3 sensitive intracellular Ca²⁺ stores. Our data indicates that p3Bax can modulate the entry of extracellular Ca²⁺, and thus regulate the amplification of apoptosis in prostate cancer cells.