Background: Cardiac rehabilitation is beneficial for patients after ST-segment elevation myocardial infarction (STEMI). However, most institutes perform outpatient training phase (phase II) of post-MI cardiac rehabilitation after 2-4 weeks. To evaluate the possibility of performing cardiac rehabilitation with an earlier schedule after STEMI. Methods: We conducted a series of early phase II cardiac rehabilitation starting from 5-7 days after STEMI, including the training group (n = 28) and the control group (n = 42). Results: The results showed an improved mental component summary of the SF-36 questionnaire after 6 months in the training group. No adverse event was noticed during this early phase II training. Conclusions: Cardiac rehabilitation after STEMI might be started earlier than previously thought for clinical use or further research.