Electronic apparatuses and adjustment methods thereof are provided. The electronic apparatus includes a camera module and a processor. The camera module is enabled into an HDR mode and captures a reference frame according to a first exposure setting, wherein the reference frame corresponds to a plurality of luminance values. The processor calculates a weighted luminance value of the reference frame according to the luminance values, generates a comparison result by comparing the weighted luminance value and a luminance target of the HDR mode, and decides a second exposure setting according to the comparison result.