The main aim of the study to find out the significance relationship between in cognitive ability and academic achievement of higher secondary school students. Cognitive ability is a term used in cognitive psychology to define the way persons think, perceive and recall information. The school and teacher have a great extend for developing cognitive ability. The present study is about to understand the cognitive ability and academic achievement of higher secondary school students in Salem district of Tamil Nadu. Simple random Sampling method is used to collect the sample. Two fifty higher secondary school students from different types of schools like government, government aided and private were taken for the study. Cognitive ability tool was used to collect the data. For the purpose of analysis level, ‘t’ test and correlation were used. The findings of the study obtained that the there was significant relationship between cognitive ability and academic achievement of higher secondary school students.