Background: QTc prolongation is an adverse effect of COVID-19 therapies. The use of a handheld device in this scenario has not been addressed. Objectives: To evaluate the feasibility of QTc monitoring with a smart device in COVID-19 patients receiving QTc-interfering therapies. Methods: Prospective study of consecutive COVID-19 patients treated with hydroxychloroquine +/- azithromycin +/- lopinavir-ritonavir. ECG monitoring was performed with 12-lead ECG or with KardiaMobile-6L. Both registries were also sequentially obtained in a cohort of healthy patients. We evaluated differences in QTc in COVID-19 patients between three different monitoring strategies: 12-lead ECG at baseline and follow-up (A), 12-lead ECG at baseline and follow-up with the smart device (B), and fully monitored with handheld 6-lead ECG (group C). Time needed to obtain an ECG registry was also documented. Results: One hundred and eighty-two COVID-19 patients were included (A: 119(65.4%); B: 50(27.5%); C: 13(7.1%). QTc peak during hospitalization did significantly increase in all groups. No differences were observed between the three monitoring strategies in QTc prolongation (p = 0.864). In the control group, all but one ECG registry with the smart device allowed QTc measurement and mean QTc did not differ between both techniques (p = 0.612), displaying a moderate reliability (ICC 0.56 [0.19-0.76]). Time of ECG registry was significantly longer for the 12-lead ECG than for handheld device in both cohorts (p < 0.001). Conclusion: QTc monitoring with KardiaMobile-6L in COVID-19 patients was feasible. Time of ECG registration was significantly lower with the smart device, which may offer an important advantage for prevention of virus dissemination among healthcare providers.