Abstract Introduction Increased slow-wave activity (SWA) following sleep loss is a well-established physiological marker of increased sleep pressure. Recent research found SWA changes in response to sleep loss partially accounted for next-day decrements in positive affect (Finan et al., 2015; 2017). To our knowledge, however, this line of inquiry has been limited to adults. Recently, we found greater SWA during a night of healthy sleep predicted greater next-day positive emotion among pre-pubertal children (Rech et al., 2022). Here, we explored whether SWA during the second of two nights of partial sleep restriction predicted next-day emotional responses in the same cohort. Methods N=24 healthy, unmedicated children (7 to 11 years) completed a baseline assessment and one night of at-home PSG monitoring (10 hours in bed). Ten days later, children completed one night of at-home sleep restriction (7-hour sleep opportunity) followed by one night of in-lab sleep restriction with PSG monitoring (6-hour sleep opportunity). The next day, children completed an in-lab emotional assessment where they provided arousal and valence ratings in response to positive affective images from the International Affective Picture System (IAPS). Results Controlling for age and total sleep time during the first sleep restriction night, hierarchical multiple regression analyses examined if N3 SWA in frontal, central, and occipital regions during the second sleep restriction night predicted IAPS ratings. In separate models, both frontal, F(1,20)=8.535, p=.008, and occipital SWA density, F(1,20)=12.313, p=.002, predicted valence ratings in response to positive images (where lower scores indicated more positive valence). Conclusion While preliminary, findings indicate relationships between “rebound” SWA after sleep restriction and next-day emotional functioning in pre-pubertal children. Findings suggest that, prior to the pubertal transition, trait-based differences in homeostatic sleep pressure and recovery from sleep loss might alter emotional responding, potentially influencing risk for later mood disturbances. Support (if any) This research was supported by NIMH grant #R21MH099351 awarded to C.A.A.