Methuosis is a novel nonapoptotic mode of cell death characterized by vacuole accumulation in the cytoplasm. In this article, we describe a series of azaindole-based compounds that cause vacuolization in MDA-MB-231 cells. The most potent vacuole inducer, compound 13 (compound 13), displayed differential cytotoxicities against a broad panel of cancer cell lines, such as MDA-MB-231, A375, HCT116, and MCF-7, but it did not inhibit the growth of the nontumorigenic epithelial cell line MCF-10A. A mechanism study confirmed that the cell death was caused by inducing methuosis. Furthermore, compound 13 exhibited substantial pharmacological efficacy in the suppression of tumor growth in a xenograft mouse model of MDA-MB-231 cells without apparent side effects, which makes this compound the first example of a methuosis inducer with potent in vivo efficacy. These results demonstrate that methuosis inducers might serve as novel therapeutics for the treatment of cancer.