<p>Adolescents and young adults account for a large proportion of new HIV cases, and this age subgroup has worse outcomes across the HIV care continuum than adults. The lack of harmonization of data elements from implementation science trials is an important barrier that limits the learning across settings and the ability to accelerate adoption of effective implementation strategies. We aim to close this gap by assessing the ability to harmonize data elements across seven studies in the Prevention and Treatment through a Comprehensive Care Continuum for HIV-affected Adolescents in Resource Constrained Settings (PATC³H) consortium. The PATC³H team initiated a collaborative process to prospectively develop harmonized measures and then retrospectively implement additional harmonization based on data collected. We harmonized items on socio-demographic characteristics (12 items), economic stress (8 items), social support (12 items), sexual behaviors (20 items), mental health (24 items), substance use (33 items), HIV care continuum (11 items), and implementation science (126 items) for two or more of the studies. We present analysis of selected harmonized measures that revealed similarities and differences across studies which will be important to consider in future comparative assessments. Key lessons learned are that flexibility is required to collect measures across multiple settings, specifying minimum sample sizes will support meaningful analysis and identifying core measures can help prioritize data elements that can be consistently collected. The PATC³H consortium collaboration has shown that it is feasible to collect harmonized data across implementation science trials and future studies can build on these harmonization efforts.</p>