Background: Waist-to-hip ratio (WHR) is a strong predictor of mortality in patients with heart failure (HF). However, common WHR trajectories are not well established in HF with mid-range ejection fraction (HFmrEF) persons, and their relationship to clinical outcomes remains uncertain. Method: We prospectively enrolled 1,396 participants with HFmrEF (left ventricular ejection fraction 40–49%) from April 2013 through April 2017. The waist and hip circumferences of the subjects were measured at regular intervals, and the WHR was calculated as waist circumference divided by hip circumference. Latent mixture modeling was performed to identify WHR trajectories. We then used Cox proportional-hazard models to examine the association between WHR trajectory patterns and incident HF, incident cardiovascular disease (CVD), and all-cause mortality. Results: We identified four distinct WHR trajectory patterns: lean-moderate increase (9.2%), medium-stable/increase (32.7%), heavy-stable/increase (48.0%), and heavy-moderate decrease (10.1%). After multivariable adjustment, the heavy-stable/increase and heavy-moderate decrease patterns were associated with an increased all-cause mortality risk (heavy-stable/increase: adjusted hazard ratio [HR] 3.18, 95% confidence interval [CI] 2.75–4.62; heavy-moderate decrease: adjusted HR 2.32, 95% CI 1.71–3.04), incident CVD risk (heavy-stable/increase: adjusted HR 4.03, 95% CI 2.39–4.91; heavy-moderate decrease: adjusted HR 3.05, 95% CI 2.34–4.09), and incident HF risk (heavy-stable/increase: adjusted HR 2.72, 95% CI 2.05–3.28; heavy-moderate decrease: adjusted HR 2.39, 95% CI 1.80–3.03) with reference to the lean-moderate increase pattern. Conclusion: Among patients with HFmrEF, the trajectories of WHR gain are associated with poor outcomes. These findings highlight the importance of abdominal fat accumulation management during the progression of HFmrEF.