In the last years, there has been a growing interest in the brain-heart connection. A core aspect of this connection appears to be the autonomic nervous system, particularly through the vagus nerve. Accordingly, vagally mediated heart rate variability (vmHRV) is currently considered as an index of top-down control processes involved in cognition and emotion regulation. Recent evidence indicates that higher vmHRV is associated with enhanced cognitive performance across multiple domains, such as executive functions, memory, attention, and language skills. From this premises, this study examined the relationship between cardiac vagal tone, as indicated by heart rate variability (vmHRV), and cognitive functions. A sample of 143 healthy young adults completed a comprehensive neuropsychological battery. The results revealed a strong correlation between resting vmHRV and cognitive functions, particularly in executive processes. Participants with higher resting vagal tone showed superior cognitive performance in tasks requiring cognitive control, motor and cognitive inhibition, cognitive flexibility, and working memory in comparison to those with lower resting vagal tone. Furthermore, vagal-mediated heart rate variability was also found to be associated with memory, attention, and executive performance. The current research provides new insights into the interactions between cognitive and autonomic systems, further supporting evidence for body-brain interactions.