Purpose of Review <p>Worsening renal function (WRF) frequently occurs in acute heart failure (AHF) and represents a clinical challenge, as it may lead to inappropriate alterations in therapy. Understanding its mechanisms and prognostic implications is essential for optimization of treatment.</p> Recent Findings <p>The prognostic impact of WRF depends on clinical context. WRF is associated with poor outcomes when residual congestion persists; however, it is not harmful if effective decongestion is achieved. Systemic processes such as inflammation and oxidative stress may contribute to WRF with adverse outcomes, as demonstrated by novel biomarkers. Conversely, the initial decline in glomerular filtration rate observed following the initiation of heart failure therapies is typically a benign physiological response.</p> Summary <p>This review outlines the concept, pathophysiology, prognosis, and management of WRF in AHF. Clinicians should carefully interpret the clinical context of WRF and avoid the premature discontinuation of heart failure therapies to ensure optimal therapeutic decision-making.</p>