Placement testing is a crucial issue in Japanese universities. In the majority of language programs, classes are streamed by proficiency levels based on students' placement test score for efficient instruction because university students' proficiency levels vary greatly even in the same program. The Visualizing English Language Competency Test® [VELC Test® (VELC Research Group, 2013)] was designed particularly for making Japanese university students' proficiency and placement decisions. This study provides a validity argument for the VELC Test® score interpretations and uses using Kane's (2006) argument-based validity framework when administered to 4407 Japanese university students as a placement test. Four inferences from observation to decision were adequately made due to the facts that: (a) most of the VELC Test® items were working as placement items (scoring), (b) the VELC Test® (k = 120) was reliable with the small amount of error (generalization), (c) test-takers' VELC Test® score could show what they could do with their English (extrapolation), and (d) the VELC Test® could be used to separate test-takers' proficiency into three levels and could be useful for test-takers' further learning (decision). This study indicated that administrators could make valid Japanese university students' placement decisions with this test.