Introduction Cardiac auscultation skills have proven difficult to train and maintain. The authors investigated whether using phonocardiograms as visual adjuncts to audio cases improved first-year medical students’ cardiac auscultation performance. Methods The authors randomized 135 first-year medical students using an email referral link in 2018 and 2019 to train using audio-only cases (audio group) or audio with phonocardiogram tracings (combined group). Training included 7 cases with normal and abnormal auscultation findings. The assessment included feature identification and diagnostic accuracy using 14 audio-only cases, 7 presented during training, and 7 alternate versions of the same diagnoses. The assessment—administered immediately after training and repeated 7 days later—prompted participants to identify the key features and diagnoses for 14 audio-only cases. Key feature scores and diagnostic accuracy were compared between groups using repeated measures ANOVA. Results Mean key feature scores were statistically significantly higher in the combined group (70%, 95% CI 67–75%) compared to the audio group (61%, 95% CI 56–66%) (F(1,116) = 6.144, p = 0.015, d s = 0.45). Similarly, mean diagnostic accuracy in the combined group (68%, 95% CI 62–73%) was significantly higher than the audio group, although with small effect size (59%, 95% CI 54–65%) (F(1,116) = 4.548, p = 0.035, d s = 0.40). Time on task for the assessment and prior auscultation experience did not significantly impact performance on either measure. Discussion The addition of phonocardiograms to supplement cardiac auscultation training improves diagnostic accuracy and heart sound feature identification amongst novice students compared to training with audio alone.