Direct and moderated connections among symptoms of inattention, High-Frequency Heart Rate Variability (HF-HRV), and reading comprehension scores were examined. Children age 7 to 12 were rated by both parents and teachers on symptoms of inattention with the Behavior Assessment System for Children. Reading was assessed with the Peabody Individualized Achievement Test, and HF-HRV was examined during a Stroop task. Controlling for reading recognition scores, results were consistent with previous work, showing HF-HRV was significantly negatively associated with reading comprehension, with lower HF-HRV predicting higher reading scores. HF-HRV also significantly moderated the relationship between symptoms of inattention and reading comprehension, suggesting that as symptoms of inattention increase, children with low HF-HRV had higher reading comprehension scores. Variations in parasympathetic reactivity may help explain reading comprehension heterogeneity for children with symptoms of inattention.