© 2022, Yuzuncu Yil Universitesi Tip Fakultesi. All rights reserved.JT and JTp intervals are among the ventricular repolarization parameters and prolongation, just as the Q T interval is related to ventricular arrhythmias. This study aims to examine the effect of hydroxychloroquine on JTc and JTpc intervals in individuals hospitalized with COVID-19. We involved 130 COVID-19 patients divided into two groups as the hydroxychlor oquine treatment group and the control group, in this study. ECGs of the patients were recorded at admission and after a median of 48 hours following the initiation of hydroxychloroquine treatment. Then, QTc, JTc, and JTpc intervals were measured. Patients’ average age was 48 (37-66 IQR), and 53% of the individuals were female. The median basal JTpc interval was 215 ms(195-230 IQR), while JTpc-Day 3 was 220 ms(195-238 IQR). The median basal JTc interval was 320 ms(301-334 IQR), while JTc-Day 3 was 328 ms(306-343 IQR). JTpc and JTc interval in the hydroxychloroquine group have prolonged significantly (p<0.001), while there were no significant changes in the control group for both values (p>0.05). There was a significant prolongation in the multivariable linear regression analysis in JTc-Day 3 and JTpc-Day 3 after hydroxychloroquine treatment. (ß=-2.589, 95%CI, 2.384-17.894, p=0.011, ß=2.195, 95%CI, 759-14.752, p=0.030, respectively). In this study, we found significant prolongation in JTc and JTpc intervals i n the patients who take hydroxychloroquine treatment.