Carbon nanotubes (CNT), core-sheath CNT/reduced graphene oxide nanoribbon (RGONR), CNT/RGO composite, and RGO fibers have been compared as counter electrodes to fabricate novel dye-sensitized solar cells. For the I-/I-3(-) electrolyte, the core-sheath CNT/RGONR fiber shows the best catalytic activity, which in turn produces the highest energy conversion efficiency of 5.64%. In contrast, for the organic T-/T-2 electrolyte, the highest energy conversion efficiency has been produced from the CNT fiber counter electrode with the maximal value of 4.78%. The different electrocatalytic activities among these four carbon nanostructured fibers on the two typical electrolytes of I-/I-3(-) and T-/T-2 have been carefully investigated in this work.