The main objective of the study is to find out the relationship between thinking styles and academic achievement of XI standard students. Thinking Styles Inventory constructed by Sternberg (2007) was used to collect the relevant data. Marks obtained in quarterly examinations of XI standard students have been taken for estimating their academic achievement. The sample consists of 339 XI standard students of whom 177 are male and 162 are female. The data are analysed by 't' test and Karl Pearson's product moment correlation. The results indicate that there is no significant relationship between idealistic, pragmatic and analytic thinking styles and academic achievement of XI standard students. There is significant relationship between synthetic and realistic thinking styles and academic achievement of XI standard students.