This research was aimed at developing a scale for measuring the cognitive flexibility of adolescents. This scale will help us to understand how flexible individuals are in regard to themselves, others, and the environment. It consists of 19 items and is in the form of semantic differentials. Reliability and validity were tested using a sample of 637 adolescents. The Cognitive Flexibility Scale (CFS) was prepared so it was parallel to the structure of the 3 dimensions of semantic differential scales. The 3 dimensions in the CFS explain 51.33% of total variance of the scale. The internal consistency for the scale was found to be .92. Item-total correlations of the items were between .49 and .63. Test-retest correlation coefficiency within an eight-week interval was .77, and the split-half coefficiency was .87. In the criterion validity tests of the scale, the divergent validity was tested by means of the Dysfunctional Attitude Scale (Weissman & Beck, 1978). The correlation between the two scales was found to be -.44.