A DC-DC converter and a method for estimating output current of a DC-DC converter are provided. The method includes measuring, by a controller, input voltage and output voltage of the DC-DC converter and measuring output voltage of a current transformer (CT) included in the DC-DC converter. In addition, the method includes compensating, by the controller, for the output voltage based on the relationship between the measured output voltage and CT output voltage and compensating for the input voltage by measuring the input current of the DC-DC converter based on the output current of the DC-DC converter into the CT output voltage converted through the current transformer and using an output current map composed of the output voltage and the measured CT voltage. In addition, the output current is estimated using the compensated output voltage and input voltage.