A select blend of herbal extracts, Zyflamend, inhibits tumour growth via multiple mechanisms that arise through synergistic interactions between individual components. The objective in this study was to determine if the antiproliferative effects are mediated, in part, through the activation of AMPK signalling and inhibition of its downstream targets, lipogenesis and mTORC1 complex. By increasing the phosphorylation of AMPK in CWR22Rv1 and PC3 prostate cancer cell lines, Zyflamend decreased de novo lipid biosynthesis by decreasing the activity of acetyl-CoA carboxylase and the expressions of fatty acid synthase and SREBP-1c, with a concomitant up regulation of fatty acid oxidation. In addition, via AMPK, Zyflamend inhibited the activity of mTORC1 complex by directly phosphorylating raptor. Treatment with AICAR (activator of AMPK), siRNA knockdown, pharmacological inhibition, and overexpression of AMPK were used to confirm the up regulation of AMPK by Zyflamend. These results suggest that Zyflamend inhibited tumour cell proliferation via up regulation of AMPK signalling.