Background: Heart failure can be classified into chronic heart failure and acute heart failure. Rapid onsets or worsening symptoms characterize acute heart failure, while progressive symptoms characterize chronic heart failure. Exercise-based cardiac rehabilitation is recommended for chronic heart failure patients, yet controversies on whether early exercise is safe and advantageous for acute heart failure patients remain unclear. Objectives: We performed a systematic review and meta-analysis to explore the effects of early exercise on cardiac rehabilitation-related outcome in acute heart failure patients. Methods: We searched PubMed, Web Of Science, Embase, the Cochrane Library, CINAHL, PsycINFO, China National Knowledge Infrastructure (CNKI), Chinese Science and Technology Periodical Database (VIP), Wanfang Dataset and SinoMed Dataset (from the earliest date available to August 2021) for randomized controlled trials that evaluated the effects of early exercise in acute heart failure patients. Studies were selected according to inclusion and exclusion criteria. Data synthesis was performed with Review Manager 5.2. Results: 13 studies met the study criteria, including 1466 patients. Compared to the control group [routine care], early exercise improved 6 min walk distance[mean difference = 33.10, 95% CI (31.43, 34.77), P < 0.001], short physical performance battery scores[mean difference = 1.40, 95% CI (1.36, 1.44), P < 0.001], N-terminal pro-B-type natriuretic peptide[mean difference = -58.84, 95% CI (-89.25, -28.43), P < 0.001], quality of life assessed by Minnesota heart failure quality of life questionnaire [mean difference = -6.55, 95% CI (-9.99, -3.11), P = 0.0002], quality of life assessed by Kansas city cardiomyopathy questionnaire [mean difference = 7.00, 95% CI (6.58, 7.42), P < 0.001], activities of daily living [mean difference = 4.43, 95% CI (2.20, 6.65), P < 0.001], and all-cause related readmission rate [mean difference = 0.69, 95% CI (0.51, 0.94), P = 0.02]. No significant difference in left ventricular ejection fraction [mean difference = 1.93, 95% CI (-2.19, 6.05), P = 0.36], heart failure-related readmission rate [mean difference = 0.76, 95% CI (0.50, 1.17), P = 0.21] and all-cause mortality [mean difference = 0.63, 95% CI (0.18, 2.24), P = 0.47] was found between early exercise group and control group. No adverse events occurred during the intervention. Conclusion: Compared to routine care, early exercise could significantly improve the effect of physical capacity, physiological outcomes and clinical outcomes in acute heart failure patients, and appeared to be safe.