The gold nanoparticles inlaid mesoporous titania nanoparticles (Au@MTNs) thin films are fabricated on a conductive plastic substrate by using a low-temperature electrophoretic deposition (EPD) process followed by a compression post-treatment. The obtained Au@MTNs electrode exhibits an excellent light trapping because of the formation of surface plasmons on the Au nanoparticles (NPs). The flexible Au@MTNs electrodes are applied for the photoanodes in all-plastic-based dye-sensitized solar cells (DSSCs). The Au@MTNs photoanodes containing various wt% of Au NPs are prepared in order to optimize the performance of the DSSCs. When 0.8 wt% of Au NPs is used in the Au@MTNs photoanode, a power conversion efficiency (η) of 5.62% is achieved under the illumination of 100 mW cm−2, which exhibits a 14% increase compared to the DSSC fabricated with pure a titanium dioxide (TiO2) photoanode (4.93%); this enhancement is attributed to the plasmonic light trapping provided by the Au NPs.