Background <p>Long-term COVID-19 (LC), which may affect the autonomic nervous system (ANS), is the term for the symptoms that some patients had for an additional month after contracting the virus. Therefore, during the LC phase, ANS status was evaluated in patients with mild-to-moderate COVID-19 using heart rate variability (HRV), a measurement of ANS function.</p> Methods <p>A cross-sectional research with 173 participants - both positive and negative for COVID-19 – was conducted. Based on self-reports, patients with COVID-19 were classified as to whether they had LC or not. A 5-minute ECG recorder and data detection and response report were used to measure the ANS.</p> Results <p>There were notable age differences across the groups (<i>p</i> = 0.034). Patients with LC under 25 years of age had a lower HRV categorized as a very-low-frequency (VLF) domain (<i>p</i> = 0.012). Compared to the group without LC, a higher number of people in the LC group had aberrant autonomic neuroactivity (<i>p</i> = 0.048).</p> Conclusion <p>Mild-to-moderate patients with COVID-19 in young to middle age may develop autonomic dysfunction one month after infection.</p>