The TOEFL Junior® tests are designed to evaluate young language students' English reading, listening, speaking, and writing skills in an English-medium secondary instructional context. This paper articulates a validity argument constructed to support the use and interpretation of the TOEFL Junior test scores for the purpose of placement, progress monitoring, and evaluation of a test taker's English skills. The validity argument is built within an argument-based approach to validation and consists of six validity inferences that provide a coherent narrative about the measurement quality and intended uses of the TOEFL Junior test scores. Each validity inference is underpinned by specific assumptions and corresponding evidential support. The claims and supporting evidence presented in the validity argument demonstrate how the TOEFL Junior research program takes a rigorous approach to supporting the uses of the tests. The compilation of validity evidence serves as a resource for score users and stakeholders, guiding them to make informed decisions regarding the use and interpretation of TOEFL Junior test scores within their educational contexts.