Sepsis, severe sepsis and septic shock are among the most common conditions handled in the emergency department (ED). According to new Sepsis Guidelines, early diagnosis and treatment are the keys to improve survival. Plasma C-reactive protein (CRP) and procalcitonin (PCT) levels, when associated with documented or suspected infection, are now part of the definitions of sepsis. Blood culture is the gold standard method for detecting microorganisms but it requires too much time for results to be known. Sensitive biomarkers are required for early diagnosis and as indexes of prognosis sepsis. CRP is one of the acute phase proteins synthesized by the liver: it has a great sensitivity but a very poor specificity for bacterial infections. Moreover, the evolution of sepsis does not correlate with CRP plasma changes. In recent years PCT has been widely used for sepsis differential diagnosis, because of its close correlation with infections, but it still retains some limitations and false positivity (such as in multiple trauma and burns). Soluble CD14 subtype (sCD14-ST), also known as presepsin, is a novel and promising biomarker that has been shown to increase significantly in patients with sepsis, in comparison to the healthy population. Studies pointed out the capability of this biomarker for diagnosing sepsis, assessing the severity of the disease and providing a prognostic evaluation of patient outcome. In this mini review we mainly focused on presepsin: we evaluate its diagnostic and prognostic roles in patients presenting to the ED with systemic inflammatory response syndrome (SIRS), suspected sepsis or septic shock.