Significance Understanding the neuronal functions of diverse RNA pathways will lead to treatments of human neurological diseases that are caused by perturbations in RNA metabolism. Two proteins, Drosha and Pasha/DGCR8, play important roles in neurons, where they are responsible for the biogenesis of many microRNAs. Here, we show that Pasha/DGCR8 also promotes the morphogenesis of neurons in developing fruit flies independently of Drosha and therefore of most microRNA production. These studies therefore illuminate a novel function of Pasha that is medically relevant, because loss of the human ortholog of Pasha may contribute to cognitive and behavioral disorders associated with DiGeorge syndrome.