Respiratory infections are well-known precipitant factors for heart failure decompensations. Nevertheless, the diagnosis of life-threatening infections, such as pneumonia, is challenging. Pneumonia and acute heart failure often display overlapping clinical findings and, in other cases, more accurate infection-related findings are missing. In recent years, procalcitonin has emerged as a promising tool for early and accurate diagnosis of pneumonia and, interestingly, for guiding antibiotic therapy in patients with acute heart failure. We discuss two cases of acute heart failure with high procalcitonin on admission and different clinical outcomes. In this setting, procalcitonin may be a useful tool for guiding antibiotic therapy. Further controlled studies are warranted.