Self-regulation is an essential component of school readiness. Although in educational contexts self-regulation is typically defined in terms of volitional processes, it also encompasses the activity of neurophysiological systems, including the parasympathetic nervous system (PNS). In a prospective longitudinal study, 102 preschoolers (M[subscript age] = 4.82 years; 52% female) completed two measures of volitional self-regulation (the gift-wrap task and a battery of EF tasks) at the beginning of their final preschool year, and then completed the Bracken School Readiness Assessment (BSRA) at year's end. Larger increases in parasympathetic function (indexed by respiratory sinus arrythmia, or RSA) during both the gift-wrap and EF tasks were correlated with better performance on the BSRA at levels approaching significance, and subsequent regression models that controlled for relevant covariates revealed robust associations between increases in RSA and improved BSRA performance (gift wrap: B = 5.49, p = 0.012; EF: B = 7.77, p = 0.001). We interpret these results in light of polyvagal theory and discuss their implications for incorporating measures of parasympathetic activity into future educational neuroscience research.