The signaling scaffold oncoprotein IQGAP1 was identified as a classification and therapeutic biomarker in triple negative breast cancer (TNBC) cell lines. Here, we report that the antipsychotic drug Haldol induces novel protein-protein interactions with IQGAP1 and inhibits cell proliferation in TNBC cell lines. The identified proteins share known functions of IQGAP1 in secretion, transcription and apoptosis and provide further classification tools and potential precision therapeutic targets for Haldol in TNBC.