This article reports on the development, adaptation, and validation of the Wellbeing Holistic Assessment for Teachers (WHAT) tool with a sample of 1,659 Salvadoran teachers. El Salvador is a conflict-affected country marked by high levels of gang-related violence, which interacts with education and directly affects the wellbeing of teachers. Having a contextually grounded and validated tool is imperative to further our understanding of educator wellbeing in El Salvador and other conflict-affected settings, as it enables us to generate evidence that informs policies and interventions. In this article, we describe how we reviewed and selected the measures that comprise the WHAT tool, followed by an initial conceptualization of teacher wellbeing and a description of the experiences and challenges teachers in El Salvador are facing. We describe our process for translating and adapting the selected measures to the Salvadoran context, which included conducting cognitive interviews. The results from our exploratory factor analysis provide construct validity evidence for the internal structure of the individual measures used. The exploratory factor analysis that included all the items for all the measures confirmed that each scale is indeed measuring a different construct. The results from a confirmatory factor analysis confirmed a good model fit. The process of adapting the tool and the results of our psychometric analysis provide evidence of the tool's validity, based on the content of the items in the tool, the internal structure, and its relationship to other variables.