© 2020 American Psychological Association. Objective: The objective of the study was to evaluate a novel measure of HIV care engagement in a large sample of non-Latino White, Latino, and African American patients. The Index of Engagement in HIV care (the Index) measures the degree to which a patient feels engaged/disengaged from HIV care. However, its measurement invariance, or the degree to which observed scores can be meaningfully compared across racial/ethnic groups, has not been established. Methods: The 10-item Index is a self-report measure initially validated in the Center for AIDS Research Network of Integrated Systems cohort study. Using Center for AIDS Research Network of Integrated Systems survey data, Index scores were linked to patients' electronic medical records, which included viral load (VL) and appointment attendance data. We conducted measurement invariance analyses to test the Index's performance in the 3 racial/ethnic groups and its cross-sectional association with VL and retention in HIV care (2 primary outcomes). Results: A total of 3,127 patients completed the Index, which showed good reliability across the 3 groups (alphas >.84). Confirmatory factor analysis model fit statistics showed that the Index demonstrated configural, metric, and scalar invariance, supporting the conclusion that the Index is a single factor construct. Lastly, lower Index scores associated with a concurrent detectable VL and poor retention in HIV care for all 3 groups. Conclusion: Having demonstrated invariance, the Index scores can be used to compare engagement levels across non-Latino Whites, Latinos, and African Americans in HIV care settings. Improving HIV care retention requires tools that can accurately identify people struggling to stay engaged in HIV care, especially racial/ethnic minorities.