Introduction: Electrocardiogram (ECG) interpretation competency remains a challenge in nursing education due to the complexity of waveform analysis and clinical reasoning. Innovative instructional strategies are needed to enhance students’ clinical competencies. This study aimed to compare the effectiveness of peer-assisted learning (PAL) and animated video instruction (AVI) in enhancing ECG interpretation competency among nursing students. Methods: A quasi-experimental non-equivalent pretest-posttest trial was conducted among 110 sixth-semester nursing students in Indonesia, who were assigned to two groups: PAL and AVI. The two groups were given the same instructional content and time, but they differed in terms of learning style. ECG interpretation competency was assessed using a validated 11-item checklist. Wilcoxon signed-rank tests were used to compare the data within a group, and Mann-Whitney U tests were used to compare the data between groups. Effect sizes were calculated to determine the magnitude of the differences. Results: Both teaching strategies enhanced the ECG interpretation skills of the students. The Wilcoxon signed-rank test results for the PAL group showed a significant improvement in competency scores (Z = -6.458, p < 0.001), with an extremely large effect size (r = 0.87). In the same manner, the AVI group also showed a significant increase (Z = -6.450, p < 0.001), with a very large effect size (r = 0.87). Conclusions: PAL improved overall ECG interpretation competency and specific components more than AVI (p < 0.05). Nursing educators should prioritize PAL, with animated videos as supplementary learning tools.