Objective: To analyze the clinical value of serum 25-hydroxyvitamin D [25(OH)D], procalcitoninogen (PCT) and inflammatory index expression in neonatal infectious pneumonia (NIP). Methods: Ninety-two cases of NIP in our hospital were selected as the infected group, and the cases were collected from January 2022 to December 2024, among which 54 cases and 38 cases were classified as mild and severe according to the degree of the disease, respectively, and 92 cases of healthy newborns who were born in the same period of time in our hospital were selected as the non-infected group in the same proportion. The serum 25(OH)D, PCT and inflammatory indexes [C-reactive protein (CRP), interferon-gamma (IFN-γ), interleukin-6 (IL-6)] expression levels of the newborns in both groups were detected, and the results of the two groups were analyzed and compared with the expression levels of the indexes in the mildly ill and severely ill children with NIP, analyze the correlation. Results: Compared with the non-infected group, the infected group had lower serum 25(OH)D levels and higher levels of PCT, CRP, IFN-γ, and IL-6 (P < 0.05); compared with children with mild NIP, children with severe NIP had lower serum 25(OH)D levels and higher levels of PCT, CRP, IFN-γ, and IL-6 (P < 0.05); 25(OH)D was negatively correlated with the disease severity of children with NIP, while PCT, CRP, IFN-γ, and IL-6 were positively correlated with the disease severity of children with NIP (P < 0.05). Conclusion: The expression levels of inflammatory indicators such as serum 25(OH)D, PCT, CRP, IFN-γ, and IL-6 may abnormally increase or decrease in children with NIP, and there is a certain correlation with the severity of NIP.