Despite extensive research on assessing collocational knowledge, valid measures of academic collocations remain elusive. With the present study, we employ an argument-based approach to validate two Academic Collocation Tests (ACTs) that assess the ability to recognize and produce academic collocations (i.e., two-word units such as "key element" and "well established") in written contexts. A total of 343 tertiary students completed a background questionnaire (including demographic information, IELTS scores, and learning experience), the ACTs, and the Vocabulary Size Test. Forty-four participants also took part in post-test interviews to share reflections on the tests and retook the ACTs verbally. The findings showed that the scoring inference based on analyses of test item characteristics, testing conditions, and scoring procedures was partially supported. The generalization inference, based on the consistency of item measures and testing occasions, was justified. The extrapolation inference, drawn from correlations with other measures and factors such as collocation frequency and learning experience, received partial support. Suggestions for increasing the degree of support for the inferences are discussed. The present study reinforces the value of validation research and generates the momentum for test developers to continue this practice with other vocabulary tests.