PtO decorated multi-walled carbon nanotubes (MWCNTs) were prepared by a polymer ligand assisted strategy and applied as the counter electrode (CE) in dye-sensitized solar cells (DSCs) for the first time. Compared with the energy conversion efficiency (Eff) of Pt CE based DSCs, the DSCs with PtO–MWCNTs CE showed an overall Eff of 8.67%, giving an improvement of 12.7%. Better electrocatalytic activity towards I3−/I− redox pairs than Pt CE indicated that the PtO–MWCNTs was a promising electrocatalyst for DSCs.