The aim of this study was to compare the clinical significance of procalcitonin and presepsin levels in associationwith different bacterial species or cultures in sepsis cases that meet the Sepsis-3 criteria.Methods: We conducted a 2-year observational study of sepsis patients found to meet the Sepsis-3 criteria. Theparameters examined included age, the infection focus, the initial blood procalcitonin and presepsin levels, andthe SOFA score. The patients were divided into several groups based on bacterial cultures from blood specimensand fluid and tissue specimens taken from the infected sites.Results: Finally, 132 sepsis patients were investigated in the study period. The patients had a mean age of 73.3, amean SOFA score of 8.9, and mean blood procalcitonin and presepsin levels of 35.6 ng/ml and 1319.6 pg/ml,respectively. The patients were divided into a culture/positive group (n = 108) and a culture/negative group (n =24) based on the bacterial specimen cultures. The culture/positive group, which included duplicate cases, wasfurther divided into a blood/positive group (n = 63) and a local infection group (n = 86). No significant differencesin the SOFA score were observed among the culture groups. Blood procalcitonin was significantly lower in theculture/negative (p < 0.0001) and blood/negative groups (p < 0.0152). The blood presepsin level, however, didnot significantly differ between those groups.Conclusions: The blood procalcitonin levels in sepsis patients diagnosed according to the Sepsis-3 criteria maybe lower when the bacterial specimen cultures are negative. In such patients, reliance on procalcitonin alone forclinical guidance may lead to an underestimation of sepsis severity.