The study aimed at ascertaining the validity and reliability of business studies achievement test for senior secondary schools in Nigeria. The study adopted an instrumentation design. The area of the study was Anambra State. The population of the study consisted of all the 23,077 students and 586 business studies teachers in two hundred and sixty-one senior secondary schools in Anambra State. Multi-stage sampling techniques involving two stages were adopted for this study. Thus proportionate stratified and purposive sampling techniques were employed at the first and second stages respectively. This was used to determine the sample size of the study, which was 630 made up of 393 students in senior secondary school one and 238 business studies teachers in Anambra State. The instrument Business Studies Acheivement Test (BSAT) was face validated by five experts, while the content validation was carried out by using a table of specifications which consisted of content areas and behavioral objectives structured after Bloom's taxonomy of cognitive domain. To generate items for Business Studies Achievement Test, the instruments were distributed to 238 business studies teachers by the researcher and his assistants in their respective schools during the 2021/2022 session. Business Studies Acheivement Test (BSAT) was used for data collection, the BSAT was a single multiple-choice objective test with an expected response of either pass (1) or fail. This helped in determining the construct validity of the instrument as well generating items for the business studies achievement test. The generated instrument was pilot tested in six secondary schools in the six educational zones in Anambra state. The developed instrument was found to be valid and reliable with an estimate of 0.96 obtained for placing students in business studies in senior secondary schools in Nigeria. Based on the findings of the study it was recommended that teachers, researchers, and relevant agencies should Relevant educational agencies, teachers, researchers should endeavor to establish the validity of any instrument they develop for any educational purpose to ensure the items are valid and relevant to the subject objective also instrument for educational purposes should be reliable, this will facilitate the better decision for students’ placement and achievement.