The present application provides an under-display camera assembly, including: an organic light-emitting diode display screen, wherein a display region of said display screen includes an under-display camera region and a non-under-display camera region, and a pixel density of the under-display camera region is configured to be less than that of the non-under-display camera region; and a camera module located at a rear end of the under-display camera region, and including an iris diaphragm, a lens group, and a photosensitive component, wherein the iris diaphragm is provided between a bottom surface of a pixel light-emission layer and a top surface of the foremost lens of the lens group, and has a closed state and a transmission state. The iris diaphragm, in the closed state, reflects light from the display screen or emits light by itself from the front of the display screen, and the transmission state refers to a state in which a light path of the camera module is opened. The application further provides a corresponding terminal device. The application can produce full-screen display effects, provide an added aperture adjustment function, and facilitate alignment during an assembly process.