Every student has potential for higher-order thinking. The key is to unlock the world of mathematics through a student's natural inclination to strive for purpose and meaning. Reasoning is fundamental to the knowing and doing of mathematics. The present study aims to find out the relationship between reasoning ability and achievement in mathematics of higher secondary students. Fifty five, higher secondary students were randomly selected as sample. Survey method was adopted for the study. The data was collected using a test on reasoning ability (RA). Critical ratio(t-test), chi-square test and Pearson’s product moment correlation were applied to test the hypotheses. Interpretations were drawn based on the findings. Reasoning ability of the higher secondary students was found to be an average and there was a high positive correlation between reasoning ability and achievement in mathematics.
