Many of the primary clinical manifestations of heart failure are due to fluid retention and congestion, and therefore treatments targeting congestion play a central role in heart failure management. Diuretic therapy remains the cornerstone of congestion treatment, and diuretics are prescribed to the majority of heart failure patients. Despite this ubiquitous use, there is limited evidence from prospective randomized studies to guide the use of diuretics. Some observational data have suggested that diuretics may actually be harmful in heart failure, potentially contributing to worsening renal function, neurohormonal activation, and even heart failure progression. Recent clinical trial data have provided new insights into the balance of risks and benefits from diuretics. This review describes the mechanism of action of available diuretic classes, reviews their clinical use based on current guidelines, and briefly discusses evolving alternatives to diuretic therapy in the management of congestion in heart failure patients.