Background and Objectives: Few studies have addressed the predictive implications of right ventricular (RV) and pulmonary arterial (PA) coupling as assessed by echocardiography in patients with acute heart failure (AHF). This study aimed to ascertain the prognostic importance of RV-PA coupling in AHF cases and discern any divergence in its prognostic efficacy based on different heart failure (HF) phenotypes. Methods: We evaluated RV-PA coupling by measuring the ratio of right ventricular global longitudinal strain (RVGLS) to pulmonary arterial systolic pressure (PASP), termed the RVGLS/PASP ratio, and assessed its prognostic role using the STrain for Risk Assessment and Therapeutic Strategies in Patients with Acute Heart Failure registry. Results: From an AHF registry of 4312 patients, we analyzed the RVGLS/PASP ratio in 2,865 patients (1,449 men; age, 71.1±13.5 years). At a median follow-up of 35.0 months, 1,199 (41.8%) patients died. Remarkably, PASP (hazard ratio [HR], 1.012; p<0.001), RVGLS (HR, 1.019; p<0.001), and the RVGLS/PASP ratio (HR, 2.426; p<0.001) were statistically significant predictors of all-cause mortality in the univariate analysis. The RVGLS/PASP ratio was a significant predictor of all-cause mortality in all the HF phenotypes, including HF with reduced ejection fraction (HR, 2.124; p=0.002), HF with mildly reduced ejection fraction (HR, 2.733; p=0.021), and HF with preserved ejection fraction (HR, 2.134; p=0.006). Multivariate analysis after adjusting for clinical and echocardiographic variables revealed that the RVGLS/PASP ratio ≤0.32 was associated with a 36% increase in all-cause mortality (HR, 1.365; p<0.001). Conclusions: Impaired RV-PA coupling, defined as an RVGLS/PASP ratio (≤0.32) was associated with an increased risk of mortality in patients with AHF across all HF phenotypes.