The inhibitor of growth (ING) family proteins have been defined as candidate tumor suppressors. ING4 as a novel member of ING family has potential suppressive effect on different tumors via multiple pathways. However, the role of adenovirus-mediated ING4 (Ad-ING4) gene therapy for human breast carcinoma remains unknown. This study investigates the therapeutic effect of Ad-ING4 on human breast cancers in vitro and in vivo in an athymic nude mouse model, using two human breast carcinoma cell lines MDA-MB-231 (mutant p53) and MCF-7 (wild-type p53) and elucidated its underlying mechanism. It was found that Ad-ING4 treatment could induce in vitro significant growth suppression in both mutant p53 MDA-MB-231 and wild-type p53 MCF-7 breast carcinoma cells despite p53 status. This study further demonstrates that Ad-ING4 gene transfer resulted in G2/M phase arrest and apoptosis, upregulated P21, P27, and Bax, downregulated Bcl-2, IL-8, and Ang-1, promoted cytochrome c release from mitochondria into cytosol, and activated caspase-9, caspase-3, and PARP in mutant p53 MDA-MB-231 breast carcinoma cells. Moreover, intratumoral injections of Ad-ING4 in nude mice bearing mutant p53 MDA-MB-231 breast tumors remarkably inhibited the human breast xenografted tumor growth and reduced CD34 expression of tumor vessels and microvessel density. This retarded MDA-MB-231 breast carcinoma growth in vitro and in vivo elicited by Ad-ING4 closely correlated with the upregulation of cell cycle-related molecules P21 and P27, decrease in the ratio of anti- to proapoptotic molecules Bcl-2/Bax, release of cytochrome c from mitochondria into cytosol followed by caspase-9 and -3 activation leading to apoptosis via intrinsic apoptotic pathway, and the reduced expression of proangiogenic factors IL-8 and Ang-1 involved in the inhibition of tumor angiogenesis. Thus, the results indicate that Ad-ING4 is a potential candidate for breast cancer gene therapy.