A display panel, a manufacturing method thereof, and a display device are provided. In the display panel, a first undercut structure and a second undercut structure are formed along a vertical direction of an overlappingly connecting hole of the first electrode layer and the auxiliary electrode layer. Therefore, an overlappingly connecting area between the first electrode layer and the auxiliary electrode layer can be enlarged. As such, the first electrode layer can be ensured to have high transparency and good conductivity, thereby solving an issue of IP drop of the first electrode. In addition, by using this undercut structure as well as using a metal line layer to overlappingly connect the first electrode layer with the auxiliary electrode layer, the overlappingly connecting area between the first electrode layer and the auxiliary electrode layer can be enlarged without reducing an aperture ratio of the display panel.