A hair treatment composition is described that contains an acetoacetylated compound. The acetoacetylated compound, for instance, can be a bis acetoacetylated compound. In one embodiment, for instance, the acetoacetylated compound comprises a bis acetoacetate or a bis acetoacetamide. In one embodiment, the hair treatment composition can be used to straighten hair. The composition is also well suited for decreasing hair frizz. The acetoacetylated compound is capable of crosslinking hair fibers upon the application of heat.