Crystal structures for the commercial monohydrate form and an anhydrate form of dasatinib, an oral anti-cancer agent, are presented along with characterization by Raman spectroscopy, powder X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. Solubility measurements conducted in water reveal the anhydrate has dramatically improved solubility compared to the commercial hydrate form. Finally, dasatinib is a rare example of a promiscuous solvate former and the basis for this behavior can now be understood by examining the poor packing efficiency in the unsolvated form.