Background Intensive care nurses play an important role in the management of critically ill patients including identification of cardiac arrhythmias. Interventions to improve arrhythmia identification can be expensive, time‐consuming, and are not always successful. Aims This study aimed to explore the effectiveness of using short message service (SMS) messaging to improve intensive care nurses' cardiac arrhythmia interpretation skills. Design This study was a prospective, two‐group, assessor‐blinded, randomized controlled trial with a pretest‐posttest experimental design. Methods The study was conducted from February 2020 to February 2021 for the intervention as well as the control group, in a teaching hospital in northwest Turkey. The intervention group was sent the one‐way SMS messages on cardiac arrhythmias via WhatsApp during an 8‐week period, whereas the control group did not receive any intervention. The Cardiac arrhythmias assessment questionnaire (CAAQ) was used to measure outcomes. The data were analysed using ANCOVA and an independent t‐test. Results A total of 66 intensive care nurses were randomly assigned to either the intervention or the control group. The ANCOVA analysis indicated that ICU nurses who received SMS messages about cardiac arrhythmias two times a week had significantly increased CAAQ scores (P < 0.001) with a large effect size (partial eta‐squared = 0.588). Conclusion This study concluded that using SMS messages as a training tool has a positive influence on cardiac arrhythmias interpretation skills among ICU nurses. Relevance to clinical practice Using SMS messages could be an alternative, effective, and innovative approach to improve nurses' clinical practice skills.