Racial difference of religiosity in a heterogeneous older population had long been a focal point of gerontological research. However, most religiosity measures were developed from homogenous sample, few underwent rigorous psychometric validation, and studies on racial difference of religiosity had been obstructed. This cross-sectional study adapted a religiosity measure originally designed for blacks only to a heterogeneous older population of blacks and whites, validated its psychometric properties, and examined racial difference of religiosity. Based on qualitative research of concepts, intensive literature review, and abundant experiences in this field, we adapted the original measure. Then, using the data collected from a survey of 196 black and white Americans 55 years and older in Charlotte, North Carolina, we investigated full-scale psychometric properties of the adapted measure at the item-, domain-, and measure- level. These psychometric validations included item analysis, item-scale correlations, correlation matrix among items, confirmatory factor analysis (CFA) to determine if the original factor structure held after adaptation, and reliability analysis using Cronbach's alpha. Finally, using Multiple Indicators and MultIple Causes (MIMIC) models, we examined racial difference of religiosity through regression with latent variables, while potential measurement bias by race through differential item functioning (DIF) was adjusted in the MIMIC models. In result, we successfully adapted the original 12-item religiosity measure for blacks into an 8-item version for blacks and whites. Although sacrificed few reliability for brevity, the adapted measure demonstrated sound psychometric properties, and retained the original factor structure. We also found racial differences of religiosity in all three domains of the measure, even after adjustment of the detected measurement biases in two domains. In conclusion, the original measure can be adapted to and validated for a heterogeneous older population of blacks and whites. Although the adapted measure can be used to measure the three domains of religiosity in blacks and whites, the observed racial differences of religiosity need to be adjusted for measurement biases before meaningful comparisons.