The present disclosure provides a COA substrate, a display device and a method for manufacturing the COA substrate. The COA substrate includes: a passivation layer pattern arranged on a first conductive layer pattern including a data line, and a source electrode and a drain electrode of a TFT, and including a first via-hole at a position corresponding to the drain electrode; a second conductive layer pattern arranged on the passivation layer pattern and including a conductive connection pattern arranged at a region defined by a gate line, the data line and the TFT, and connected to the drain electrode of the TFT through the via-hole; and a color filter layer pattern arranged on the second conductive layer pattern and including a second via-hole at a position corresponding to the conductive connection pattern.