BACKGROUND: Many commonly used drugs can prolong the QTc interval (QTc), which can lead to potentially life-threatening arrhythmias. In the current era of COVID-19 pandemic, it is worth mentioning that the disease itself and several drugs used for its treatment have been associated with QTc prolongation. OBJECTIVE: To evaluate the agreement and clinical precision of a portable single-lead ECG device to measure the QTc interval compared to the standard 12-lead ECG. METHODS: In sequential tests, QTc of ECG recordings obtained with the device KardiaMobile (KM-1L) (AliveCor(R)) were compared to QTc obtained with conventional 12-lead ECG. Agreement was evaluated using Bland-Altman plots and the Lin's concordance coefficient. Consistency between the two devices in determining QTc prolongation (QTc >/=470 ms in males, or >/=480 ms in females), was evaluated with kappa statistics. RESULTS: 128 patients with a presumed or confirmed diagnosis of COVID-19 admitted to a University Hospital were included. QTc intervals measured with KM were similar to QTc measured with conventional ECG (442.45+/-40.5 vs. 441.65+/-40.3 ms, p:0.15). Bland-Altman analysis showed no significant difference in QTc values (average difference of -0.797, 95% Limits Of Agreement:-13.179;11.585). Lin's concordance coefficient showed an excellent agreement (0.988, p<0.001). Concordance between the two devices for determining QTc prolongation was excellent (Kappa>0.90). CONCLUSION: ECG recordings obtained with KM-1L allow an accurate QTc interval assessment. Considering its simplicity of use, this approach has advantages over conventional ECG and can provide an alternative for the evaluation of QTc in hospitalized patients, during the current time of pandemic by COVID-19 and beyond.