An organic thin film transistor array panel is provided, which includes: a substrate; a data line formed on the substrate and including a source electrode; a drain electrode formed on the substrate and separated from the data line; an organic semiconductor disposed on the source electrode and the drain electrode; a gate insulator formed on the organic semiconductor; a gate line including a gate electrode disposed on the gate insulator; a passivation layer formed on the gate line and having a first contact hole on the drain electrode; a pixel electrode connected to the drain electrode through the first contact hole; and an opaque light blocking member disposed under the organic semiconductor.