Abstract: The goal of this study was to investigate the role of procalcitonin (PCT) in diagnosis of neonatal sepsis and its correlation with C-Reactive Protein (CRP). One hundred and seventeen neonates with the gestational age ≥35 weeks with clinically suspected diagnosis of neonatal sepsis were studied during one year from 2007 in Tabriz Children`s Hospital. Conventional sepsis workup was done in all cases and the diagnosis of neonatal sepsis was proved based on the results of blood culture. The serum procalcitonin was measured by quantitative Chemo-luminance methods and the results were compared with CRP levels between the neonates with and without proven sepsis. The results showed among in 117 neonates with suspected sepsis 27 (23.1%) cases have positive blood culture (proven sepsis). The mean levels of PCT in neonates with and without proven sepsis was 4.42 ±6.66 vs. 2.06 ±4.03 ng mL-1 and CRP 33.98 ±36.81 vs. 12.30 ±20.42 mg L-1 were significantly higher in neonates with proven sepsis (p = 0.026 and p <0.001). The sensitivity, specificity, positive predictive value and negative predictive value of PCT (more than 2 ng mL-1) were 66.7, 50, 28.6, 83.3 and CRP (more than 3.5 mg L-1) were 70.4, 72.2, 43.2 and 89%, respectively, in diagnosis of neonatal sepsis. There was a meaningful correlation between the level of PCT and CRP in the sepsis group (r = 0.797, p <0.001). The results of the current study showed that more relying on the level of PCT and CRP for planning the management of neonates with suspected sepsis is not logical, but a negative result may be helpful in ruling it out.