The role of the counter electrode (CE) in dye-sensitized solar cell (DSSC) is to collect electrons from the external circuit and reduce I sub(3) super(-) to I super(-) in the electrolyte. In this paper, the perovskite-phase La sub(0.5)Sr sub(0.5)CoO sub(2.91) (LSCO) nanoparticles were synthesized through a sol-gel method and used as the CE for DSSC. The cell showed a power conversion efficiency (PCE) of 3.24 %. To further improve the PCE of CE of the LSCO nanoparticles, the nanocomposites of the LSCO nanoparticles with reduced graphene oxide (LSCOGO) have been prepared via a simply physical mixing method and served as the efficient CE for DSSC. The LSCOGO nanocomposites exhibit excellent electrocatalytic performance for reduction of triiodide, owing to the positive synergetic effect between LSCO nanoparticles and RGO sheets. As a consequence, the DSSC with the LSCOGO nanocomposites CE yielded a PCE of 6.32 %, which is observably higher than that of using pristine LSCO CE (3.24 %) or RGO CE (4.54 %) alone, and up to 88 % of the Pt CE (7.18 %).