In this study we examined high frequency heart rate variability (HF-HRV, a parasympathetic index) both at rest and during challenge, to assess if variations in cardiovascular activity measured during a Stroop task could be used to predict reading achievement in typically developing children. Reading achievement was examined using the Peabody Individual Achievement Test–Revised. Results showed that greater HF-HRV suppression during both the Stroop word and Stroop word–color conflict tasks was associated with better reading achievement. Higher basal levels of HF-HRV did not predict better reading scores. These results are among the first to show a link between HF-HRV and reading achievement in a normative school age population, and offer new insight into the association between cognitive activity and autonomic regulation of the heart.