This study aims to compare different approaches to measuring racial/ethnic disparities in mental health (MH) service use among a nationwide representative sample of children referred to the child welfare system and compare the magnitude and direction of potential disparities in MH service use over time. Using data from the National Survey of Child and Adolescent Well-Being, six summary measures of disparity were implemented to quantify racial/ethnic disparities in MH service use. This study found that youth of color were less likely than their White counterparts to receive MH services. This racial/ethnic disparity was found to increase over time; however, the magnitude of the increase varied considerably across disparity measures. In addition, the estimated increases in disparity were even greater when the sample was limited to youth in need of MH services. This study shows that the same data may produce different magnitudes of disparity, depending on which metric is implemented and whether MH need is accounted for. A greater understanding of and justification for selection of methods to examine MH disparities among child welfare researchers and policy makers is warranted.