In general, the tensile forces on hanger cables of a suspension bridge play an important role in evaluating the bridge condition. Two tensile force estimation methods, which are based on a string or cable equation, have been widely applied to estimate the tensile forces by using the measured frequencies on hanger cables. However, both methods are not applicable to short hanger cables because the frequencies of short cables are severely sensitive to flexural rigidity. Thus, in this study the tensile forces of hanger cables, shorter than 10 meters, were estimated by back analysis of the cable frequencies measured from the Gwangan suspension bridge in Korea. To verify the feasibility of back analysis, the results from back analysis and existing methods are compared with the average measured tensile forces after completion. From the comparison, it can be inferred that back analysis results reasonably agree with the average measured tension of the short hanger cable after completion. Therefore, it is concluded that back analysis applied in this study can be an appropriate tool for estimating tensile forces of short hanger cables.