Background/Objectives: Sexual activity (SA) in heart failure (HF) is frequently impaired by physiological, psychological, and relational factors, often overlooked despite its impact on sexual life. This study identified predictors of SA in HF patients, specifically metabolic equivalents (METs), age, mental health, and partner communication. Methods: A cross-sectional study involved 144 married Thai patients with congestive HF from two tertiary hospitals. Participants completed questionnaires on demographics, METs (Duke Activity Status Index), mental health (DASS-21), and partner communication (Dyadic Sexual Communication Scale). Binary logistic regression analyzed the predictive value of these variables on SA. Results: Most participants reported some SA, but often with de-creased frequency and duration, and a lack of professional guidance. Significant predictors of SA included lower METs (OR = 0.362), depression (OR = 0.002), and effective partner communication (OR = 1.156). Age, anxiety, and stress were not significant predictors. Conclusions: The study concludes that lower METs and depression and enhanced partner communication are associated with reduced SA in HF patients. These findings emphasize integrating physical, psychological, and relational assessments into HF care. Routine evaluation of METs, depression, and partner communication should be incorporated into clinical protocols to facilitate targeted interventions and educational support for patients' sexual well-being.