We assessed the relationship between serum 25-hydroxyvitamin D (25(OH)D) level and community-acquired pneumonia (CAP) among Chinese children. This observational study examined children aged 3 days to 14 years (n=1582) from the Capital Institute of Pediatrics in 2009 to 2011. There were 797 children in the CAP group and 785 controls. The CAP group was divided into 2 groups: a pneumonia group and pneumonia-induced sepsis group. The serum 25(OH)D level was estimated using micro whole blood chemiluminescence. The average serum 25(OH)D level in all samples was 25.3214.07ng/mL, with the CAP group showing a lower value than the control group (P<.001). There were also significant differences between the pneumonia group and pneumonia-induced sepsis group (P<.001). In the pneumonia-induced sepsis group, significant differences in serum 25(OH)D levels were observed in children who received mechanical ventilation or presenting with multiple organ dysfunction (P<.01). All serum 25(OH)D levels in the pneumonia group and pneumonia-induced sepsis group were below normal levels, particularly in the sepsis group. A lower serum 25(OH)D level was associated with more serious symptoms in CAP children. Children with low serum 25(OH)D levels may be at higher risk of receiving mechanical ventilation and presenting with multiple organ dysfunction. These findings suggest that vitamin D supplements are beneficial for the treatment and prevention of CAP.