Introduction The interpretation of electrocardiograms (ECGs) is a critical competency for internal medicine trainees, yet time and resources to foster proficiency are limited. Methods This resident-authored ECG email curriculum for first-year residents involved 129 first-year internal medicine residents at three major academic university hospitals. Residents either received the resident-authored ECG email curriculum (intervention group) or continued standard training (control group). The curriculum involved 10 multiple-choice ECG cases emailed biweekly over the 6-month study period. All participants were asked to complete a pre- and postintervention test to assess ECG interpretation competency and attitudes. The primary outcome was improvement in ECG test performance. Results Among the 129 first-year residents participating, 21 of the 65 (32%) randomized to the intervention group and 13 of the 64 (20%) randomized to the control group completed both the pre- and posttests for analysis. While all participants’ ECG test scores improved over the study period ( p < .001), improvement did not differ between groups ( p = .860). We found that the effect of the intervention on ECG test performance varied significantly by the number of cardiology rotations an intern experienced ( p = .031), benefiting naïve learners the most. All intervention group participants who completed the posttest reported they would recommend it to a colleague. Discussion While it did not improve resident performance on an ECG posttest, this resident-authored ECG email curriculum offers a scalable way to provide trainees additional practice with ECG interpretation, with particular benefit to trainees who have not yet rotated on cardiology.