Coronavirus disease 2019 (COVID-19) continues to impact populations around the globe. Information regarding the incidences and implications of arrhythmias in COVID-19 is limited. A total of 463 patients with COVID-19 and who had at least one electrocardiogram recording from February 1 to March 19, 2020, in Wuhan Union Hospital were enrolled in the study. Arrhythmias occurred in 85 of 463 (18.4%) patients: atrial arrhythmias in 10.2%, junctional arrhythmias in 0.2%, ventricular arrhythmias in 3.5%, and conduction block in 7.3%. Compared with patients without arrhythmias, those with arrhythmias had higher mortality, both during the time from symptom onset (p < 0.001) and from admission to follow-up (p < 0.001). The frequencies of severe COVID-19 (44.7% vs. 21.2%; p < 0.001) and death (25.9% vs. 10.1%; p < 0.001) were higher in patients with arrhythmias than in those without arrhythmias. Atrial arrhythmias and ventricular arrhythmias could predict severity and mortality, their odds ratios (OR) were 4.45 (95% confidence interval [CI] 2.35 to 8.40), 5.80 (95% CI 1.89 to 17.76) respectively for severity, and were 3.51 (95% CI 1.74 to 7.08), 3.41 (95% CI 1.13 to 10.24) respectively for mortality. High levels of interleukin-6 (IL-6) and IL-10 were associated with the occurrence of arrhythmias (all p < 0.05). Arrhythmias were significantly associated with COVID-19 severity and mortality. Atrial arrhythmia was the most frequent arrhythmia type. IL-6 and IL-10 levels can predict the risk of arrhythmias in COVID-19 patients.