A light shielding structure for a vertical blind is disclosed, wherein the vertical blind includes a headrail and a plurality of slats, which are hanged under the headrail in a vertical manner, and can be controlled to be turned between a shielding position and a non-shielding position. The light shielding structure includes at least one light shielding member, which is engaged to a bottom of the headrail, and can either be flipped up or naturally droop along with the turning of the slats. When the at least one light shielding member droops, gaps formed between the bottom of the headrail and a top of the slats are covered, which prevents light from leaking in therethrough.