Studies examining high intensity interval training (HIIT) and moderate intensity continuous training (MICT) have yielded conflicting findings regarding changes in left ventricular ejection fraction (LVEF) in heart failure (HF) patients with reduced ejection fraction (EF). PURPOSE: Use the meta-analytic approach to compare the effects of HIIT versus MICT on LVEF in HF patients with reduced EF. METHODS: A search for studies published up to July 2018 was conducted using four electronic databases: PubMed, Academic Search Complete, SportDiscus and ScienceDirect. Studies were included if they met the following criteria: (1) clinical trials, (2) studies that reported means and standard deviations for LVEF, (3) adult men and women 18 years of age and older with a previous diagnosis of HF and an ejection fraction <55%, and (4) studies published in English or Spanish. Change outcome effect sizes (ES) using the original metric were calculated from each study. Results were pooled using random-effects models. A two-tailed alpha value <0.05 was considered statistically significant. Heterogeneity was assessed using the Q statistic and inconsistency using I². Small-study effects was examined using funnel plots and influence analysis was conducted with each study deleted once. RESULTS: Of the 235 studies screened, 12 trials representing 418 HF patients met the criteria for inclusion. The number of sessions ranged from 24-48 and duration from 28-47 minutes per session. Overall, HIIT significantly increased LVEF (ES = 6.4%, 95% CI = 3.7% to 9.1%; p <0.001). No statistically significant changes were found for either MICT (ES = 3.1%, 95% CI = -0.4% to 6.7%; p = 0.08) or Controls (ES = -0.8%, 95% CI = -1.8% to 0.2%; p = 0.11). Statistically significant heterogeneity and a moderate amount of inconsistency was found for HIIT (Q = 18.4, p=0.02; I² = 56.5%), statistically significant heterogeneity and a large amount of inconsistency for MICT (Q = 42.9, p < .001; I² = 79.0%), but no statistically significant heterogeneity or inconsistency for Controls (Q = 0.42, p = 0.81; I² = 0%). Small-study effects were observed for both HIIT and MICT but not Controls. With each study deleted from the models once, changes ranged from 5.5% to 7.9% for HIIT, 1.9% to 3.6% for MICT, and -3.0% to 0.4% for Controls. CONCLUSION: HIIT increases LVEF in HF patients with reduced EF.