This study aims to develop a valid and reliable achievement test to measure the achievement of eighth-grade students in the "Seasons and Climate" unit of the science course. The research was carried out using a survey model. The study group consists of 298 eighth-grade students studying in various cities in Turkey in the 2020-2021 academic year. The content validity of the prepared questions was examined with a table of specifications. An achievement test of 25 questions was obtained by making item analyses with the data obtained from the pre-pilot study. After the pilot study of this test, the reliability analysis of the test was made, and the KR-20 internal consistency coefficient was 0.88; the KR-21 internal consistency coefficient was determined to be 0.86. In addition, while the mean item difficulty index of the test was 0.61, the mean discrimination index was calculated as 0.50. As a result, a valid and reliable achievement test was obtained for the metacognitive learning outcomes of the "Seasons and Climate" unit in the eighth grade 2018 science curriculum. In addition, since the science curriculum of the Ministry of National Education is updated from time to time according to international developments, it is possible to say that the achievement test developed is for international readers. In the way followed in this study, researchers can develop multiple-choice achievement tests that measure metacognitive learning outcomes for different subjects.