Members of the Wiscott–Aldrich syndrome protein (WASP) family bind to and subsequently activate the actin-related protein 2 and 3 (Arp2/3) complex and, together, these proteins are key mediators of actin polymerisation. Neural-WASP (N-WASP) activity is regulated by a number of different mechanisms, including through its interaction with phosphoinositides and small GTPases, tyrosine phosphorylation and an intramolecular interaction between its GTPase-binding (GBD), and verprolin, cofilin and acidic (VPA) domains. Kwang Chul Chung and co-workers (p. 67) now report an additional N-WASP regulatory mechanism that involves the proline-directed serine/threonine kinase DYRK1A (dual-specificity tyrosine-phosphorylation-regulated kinase 1A). They show that DYRK1A interacts with N-WASP and phosphorylates three threonine residues (Thr196, Thr202 and Thr259) in the DYRK1A GBD. This phosphorylation strengthens the interaction between the GBD and the VCA domain and locks N-WASP in an autoinhibited conformation that inhibits Arp2/3-mediated actin polymerisation. The overexpression of phosphomimetic N-WASP mutants inhibits the formation of filopodia and dendritic spines in COS-7 cells and primary hippocampal neurons, respectively. The authors conclude that, through phosphorylating N-WASP, DYRK1A contributes to the regulation of actin-based cellular processes.