The objective of this study was to determine the extent to which constitutive skin color explains racial/ethnic differences in serum 25-hydroxyvitamin D (25OHD) concentrations in urban schoolchildren. Analysis of covariance (ANCOVA) was used to determine associations of 25OHD with parent-reported race/ethnicity and constitutive skin color as measured by reflectance colorimeter [individual typology angle (ITA°; higher value corresponds to lighter skin)] in 307 Greater Boston schoolchildren aged 9-15 during October-December 2011. Nearly 60% of all children were inadequate in 25OHD (<20 ng/mL). Prevalence of inadequate 25OHD differed by race/ethnicity (p<0.001): white (46.6%), black (74.5%), Hispanic (64.7%), Asian (88.9%), and multi-racial/other (52.7%). Serum 25OHD increased 0.6 ng/mL per 10° increase in ITA° value (p<0.001). The prediction of 25OHD by race/ethnicity was slightly stronger than the prediction by skin color in separate models (R2=0.19, R2=0.16, respectively). Most of the variability in 25OHD in race/ethnicity was due to constitutive skin color in this group of racially diverse US children.