A cationic amphiphile, cholest-5en-3β-oxyethyl pyridinium bromide (PY+-Chol), is able to efficiently disperse exfoliated graphene (GR) in water by the physical adsorption of PY+-Chol on the surface of GR to form stable, dark aqueous suspensions at room temperature. The GR–PY+-Chol suspension can then be used to solubilize Tamoxifen Citrate (TmC), a breast cancer drug, in water. The resulting TmC–GR–PY+-Chol is stable for a long time without any precipitation. Fluorescence emission and UV absorption spectra indicate the existence of noncovalent interactions between TmC, GR, and PY+-Chol in these suspensions. Electron microscopy shows the existence of segregated GR sheets and TmC ‘ribbons’ in the composite suspensions. Atomic force microscopy indicates the presence of ‘extended’ structures of GR–PY+-Chol, which grows wider in the presence of TmC. The slow time-dependent release of TmC is noticed in a reconstituted cell culture medium, a property useful as a drug carrier. TmC–GR–PY+-Chol selectively enhanced the cell death (apoptosis) of the transformed cancer cells compared to normal cells. This potency is found to be true for a wide range of transformed cancer cells viz. HeLa, A549, ras oncogene-transformed NIH3T3, HepG2, MDA-MB231, MCF-7, and HEK293T compared to the normal cell HEK293 in vitro. Confocal microscopy confirmed the high efficiency of TmC–GR–PY+-Chol in delivering the drug to the cells, compared to the suspensions devoid of GR.