Williams syndrome transcription factor (WSTF) has emerged as an incredibly versatile nuclear protein. WSTF and the ATP-dependent chromatin remodeling complexes in which it exists, WINAC, WICH, and B-WICH, have been studied in a variety of organisms. This research has revealed roles for WSTF in a number of diverse molecular events. WSTF function includes chromatin assembly, RNA polymerase I and III gene regulation, vitamin D metabolism, and DNA repair. In addition to functioning as a subunit of several ATP-dependent chromatin remodeling complexes, WSTF binds specifically to acetylated histones and is itself a histone kinase as well as a target of phosphorylation. This review will describe the three known WSTF-containing complexes and discuss their various roles as well as mechanisms of regulating WSTF activity.