Achievement tests are widely used for measuring learners’ attainment in a specific subject area. Assessment of teachers’ content knowledge can be measured through achievement tests based on the curriculum, including content for a particular level of education. This article deals with the construction and standardization of Achievement Test in Mathematics based on Diploma in Elementary Education curriculum for prospective teachers at the elementary level. It is based on Bloom’s taxonomy levels of cognitive domain: Remembering, Understanding, Applying, and Skill-based. The study employed an instrumental research design and used purposive sampling for selection of the institution. The final semester of D.El.Ed. trainees of District Institute of Education & Training, Aizawl, Mizoram, 120 in number, were chosen to administer the test. Out of 51 preliminary draft items, 13 items were rejected, and 38 items were accepted. After selecting the 38 items, the reliability of the items was determined by using the split-half method. The investigator selected the D.El.Ed. trainees of DIET, Lunglei, Mizoram, to determine the reliability of the test. The reliability of the whole test was calculated to be 0.92. Based on the expert’s judgment, it was determined that the test is valid and reliable for assessing the proficiency of the prospective teachers in mathematics. The study fills a significant gap in the availability of standardized mathematics achievement tests for prospective elementary teachers in Mizoram. The developed tool may be effectively used by teacher education institutions and researchers to assess mathematical proficiency and identify areas requiring academic support among D.El.Ed. trainees.