A display unit, an electronic device and an assembling method are provided. The electronic device includes a case and a display unit. The case includes a holding compartment. The display unit is accommodated in the holding compartment, and includes a display module, a transparent cover layer and a transparent adhesive tape. The transparent adhesive tape is configured between the display module and the transparent adhesive tape, and the transparent adhesive tape is adhered to the transparent cover layer. The transparent adhesive tape includes a flange portion extending beyond the display module, and the flange portion can be bent to secure the display unit to the case. The second surface is leaned against a back plate. The back plate comprises at least one hole. The flange portion passes through the hole and is bent to attach to a surface of the display module that is farther away from the back plate.