The cytoplasmic functions of Wiskott-Aldrich syndrome family (WAS) proteins are well established and include roles in cytoskeleton reorganization and membrane-cytoskeletal interactions important for membrane/vesicle trafficking, morphogenesis, immune response, and signal transduction. Misregulation of these proteins is associated with immune deficiency and metastasis 1-4. Cytoplasmic WAS proteins act as effectors of Rho family GTPases and polymerize branched actin through the Arp2/3 complex <up>1, 5</up>. Previously, we identified Drosophila washout (wash) as a new member of the WAS family with essential cytoplasmic roles in early development <up>6, 7</up>. Studies in mammalian cells and Dictyostelium suggest that WASH functions primarily in a multiprotein complex that regulates endosome shape and trafficking in an Arp2/3-dependent manner 8-11. However, roles for classically cytoplasmic proteins in the nucleus are beginning to emerge, in particular, as participants in the regulation of gene expression <up>12, 13</up>. Here, we show that Drosophila Wash is present in the nucleus, where it plays a key role in global nuclear organization. wash mutant and knockdown nuclei disrupt subnuclear structures/organelles and exhibit the abnormal wrinkled morphology reminiscent of those observed in diverse laminopathies 14-16. We find that nuclear Wash interacts with B-type Lamin (Lamin Dm0), and, like Lamin, Wash associates with constitutive heterochromatin. Wash knockdown increases chromatin accessibility of repressive compartments and results in a global redistribution of repressive histone modifications. Thus, our results reveal a novel role for Wash in modulating nucleus morphology and in the organization of both chromatin and non-chromatin nuclear sub-structures.