The progress and development of any country or society are intrinsically tied to the growth and well-being of its youth. Adolescence, defined by the World Health Organization (WHO) as the period between ages 10 and 19, is a crucial stage of life characterized by significant physical, mental, and emotional changes. This paper presents the findings for the process of developing and validating the Adolescence Conceptual Understanding Test (A-CUT) which can be used to measure the conceptual understanding of the adolescents. The sample includes 370 secondary school students from the 3 secondary schools of Gujarat. Six concepts selected for the test includes Self-identity, Emotional intelligence, Counselling and person-to-person relationship,  Age increase, Making decisions and solving problems and Sexual Protection of Children and POCSO Act-2012. The test include 61 items with 10 items in each component except one. The Draft A-CUT was subjected to expert validation, pre-piloting with 20 students and final piloting with 370 student for item analysis and reliability. The final A-CUT consisted of 36 test items with 6 items in each component. The test had a D.I. range of 0.25 to 0.85 and a Discrimination Index from 0.40 to above. The KR20 =0.7966 and KR21 = 0.7515 values shows a good reliability. Further the reliability coefficient using Spearman Brown Formula for Half Test was 0.78 and for Whole Test was 0.88. This confirms the high level of internal consistency across the entire test. The test can be used by the researcher to measure the conceptual understanding of the students.