Millions of patients in the world are being increasingly exposed to sepsis every year, and the rate of sepsis mortality remains high. If effective antibiotic therapy is started early, morbidity and mortality levels decrease in infections. Many previous studies indicated that the prohormone procalcitonin (PCT) is an excellent marker for sepsis and its related conditions. Procalcitonin is synthesized by a large number of tissues and organs in response to the invasion by pathogenic microorganisms and the use of PCT as a marker to improve the diagnosis of bacterial infections and guide antibiotic therapy. Procalcitonin also correlates with the extent and severity of infection, and it can be used for a prognostic marker. The aim of this review was to discuss whether serum PCT levels could be a diagnostic and/or prognostic marker in sepsis.