A lip pen assembly includes a container and a lip pen is removably inserted into the container. The lip pen has a base and a handle, the base is mounted to a neck extending from an end of the container and two light bulbs are connected to the base. A seal ring has a plurality of protrusions which extend through an end of the handle. The two light bulbs include two first poles and two second poles. A cover is removably connected to the base and has a biasing member which pushes a battery and the battery pushes the protrusions to be inserted into the base when the lip pen together with the base is removed from the container, so that the battery is in contact with the first terminals to light up the light bulbs.