In recent years, membrane androgen receptors (mARs) have been identified in prostate and breast tumor cells, and their activation by specific mAR ligands was linked to the regulation of crucial cell responses, such as cell growth, motility, and apoptosis. Analysis of the molecular signals triggered by mAR in the presence of anti-androgens has clearly differentiated mAR-dependent biological actions from those induced by the activation of the classical intracellular androgen receptors (iARs). In this review, we summarize the specific cellular events attributed to mAR activation and the experimental results on distinct non-genomic signaling cascades operating in various tumor cells independently of the iAR. Furthermore, we discuss the crucial role of actin cytoskeleton organization and signaling in mediating mAR responses. Finally, we assess the clinical impact of the reported mAR-induced apoptotic regression of prostate cancer cells both in vitro and in vivo and discuss the potential role of mAR as a novel therapeutic target.