Julie Lessard and colleagues report that ATP-dependent SWI/SNF chromatin-remodeling complex subunit SMARCD2 is essential for granulocyte development. They find that Smarcd2-deficient mice fail to generate functioning neutrophils and eosinophils, and they determine that the divergent coiled-coil 1 and SWIB domains are responsible for functional specificity during granulocyte differentiation.