A method for forming an image sensor device is provided. The method includes forming an isolation structure in a substrate. The method includes forming a light-sensing region in the substrate. The isolation structure surrounds the light-sensing region. The method includes forming a grid layer over the substrate. The grid layer is over the isolation structure and has an opening over the light-sensing region. The method includes forming a first lens in or over the opening. The method includes forming a second lens over the first lens and the grid layer.