This article presents a review of the "KeyMath-3 Diagnostic Assessment" (KeyMath-3 DA), a norm-referenced individually administered diagnostic test. This review focuses only on the KeyMath-3 DA Form-A starter kit, which includes a manual, two easels, and record forms. The KeyMath-3 DA is an updated mathematics diagnostic test with the content aligned to the current national mathematics curriculum and standards. The test provides teachers with reliable and valid information on examinees' learning performance in specific and general content areas, operations, and application of mathematics. The kits are user friendly for both examinees and examiners. However, the test is easy to administer only if the examiner gets proper training on the administration procedures and with the technical part of the kits. Significantly, as mathematics involves multiple representations in solving a problem, the standardized procedures may need to account for allowing examinees to scribble their workings on a sheet of paper for all subtests. The test supports modifications for different mathematics ability levels but it does not emphasize the use of interdisciplinary skills (e.g., reading, writing). It is not appropriate for students with limited hearing, vision, and English proficiency. Also, the test may not be suitable for students in other countries that have diverse educational and cultural backgrounds in mathematics. More items at upper grade levels (i.e., above Grade 8) should be constructed to cover the mathematics curriculum of the targeted population (i.e., 4 years 6 months to 21 years 11 months). Also, the items should have vertical and horizontal alignment across grade levels. As the United States does not have any standard national curriculum, the revision of items must consider the level of mathematics content in the curriculum of each state. Further, the blueprint for item development must consider all National Council of Teachers of Mathematics (NCTM) content standards such as reasoning and proof, communication, connections, and representation. These standards were not included in the development of the test. Despite the aforementioned limitations, overall, the KeyMath-3 DA is an appropriate instrument to assess students' general mathematical ability, especially strengths and weaknesses in different mathematics content areas.