A miniaturized lens assembly includes a front lens portion, a rear lens portion, a large diaphragm plate mounted between the front and rear lens portions, a small diaphragm plate rotatable relative to the large diaphragm plate, a shutter plate rotatable relative to the large diaphragm plate, first and second actuating elements mounted on the rear lens portion, and two pivot axles mounted between the front and rear lens portions. The miniaturized lens assembly is miniature in size, is simple in structure, and is easy to assemble.