GOLPH2 (also called GP73) is a Golgi glycoprotein, which has been identified as a novel tumor marker upregulated in various cancers, including prostate cancer (PCa). GD55 is a novel GOLPH2-regulated oncolytic adenovirus that exhibits a strong killing effect on hepatoma cells. Here, we investigate the antitumor effect of GD55 on prostate cancer stem cell (CSC)-like cells in vitro and in vivo. Prostate CSC-like sphere cells were acquired and enriched by culturing DU145, LNCap or P3 prostate cancer cells in suspension. The prostate CSC-like sphere cells were capable of self-renewal, differentiation and quiescence, displaying tumorigenic feature and chemo-resistance to 5-FU, doxorubicin and DDP. Treatment with GD55 (1, 5, 10 MOI) dose-dependently suppressed the viability of DU145 sphere cells, which was a more pronounced compared to its cytotoxic action on the parental DU145 cells. In a mouse xenograft prostate CSC-like model, intratumoral injection of GD55 markedly suppressed the growth rate of xenograft tumors and induced higher levels of cell death and necrosis within the tumor tissues. Our results demonstrate that GD55 infection exerts strong anticancer effects on prostate CSC-like cells in vitro and in vivo, and has a potential to be used in the clinical therapy of PCa.