Serotonin (5-hydroxytryptamine, 5-HT) is a critical local regulator of epithelial homeostasis in the breast and exerts its actions through a number of receptors. Dysregulation of serotonin signaling is reported to contribute to breast cancer pathophysiology by enhancing cell proliferation and promoting resistance to apoptosis. Preliminary analyses indicated that the potent 5-HT1B/1D serotonin receptor agonist 5-nonyloxytryptamine (5-NT), a triptan-like molecule, induced cell death in breast cancer cell lines. Thus, we synthesized a series of novel alkyloxytryptamine analogues, several of which decreased the viability of various human cancer cell lines. Proteomic and metabolomic analyses showed that compounds 6 and 10 induced apoptosis and interfered with signaling pathways that regulate protein translation and survival, such as the Akt/mTOR pathway, in triple-negative breast cancer cells.