It is increasingly clear that seminal sleep-affective relationships begin to take root in childhood, yet studies exploring how nighttime sleep characteristics relate to daytime affective symptoms, both in clinical and healthy populations of children, are lacking. The current study sought to explore these relationships by investigating whether trait-like and/or daily reports of affective and somatic symptoms of children with generalized anxiety disorder and matched controls relate to sleep architecture. Sixty-six children (ages 7-11; 54.4% female; 56.1% Caucasian; 18.2% biracial; 6.1% African American; 3% Asian; 16.7% Hispanic) participated including 29 with primary generalized anxiety disorder (without comorbid depression) and 37 healthy controls matched on age and race/ethnicity. Participants underwent structured diagnostic assessments including child-report measures and subsequently reported on their negative affect and somatic symptoms over the course of 1 week. Children also completed 1 night of polysomnography. Among children with generalized anxiety disorder only, greater amounts of slow wave sleep corresponded with less negative affect, and greater amounts of rapid eye movement sleep was related to more somatic complaints across the week. Similarly, for trait-like measures, more rapid eye movement sleep and shorter latency to rapid eye movement sleep were related to greater depressive symptoms in the anxious group only. The current findings suggest that physiologic sleep characteristics may contribute in direct ways to the symptom profiles of clinically anxious children. The functional relevance of such findings (e.g., how specific sleep characteristics serve to either increase or reduce long-term risk) is a vital direction for future research.