We investigated an effect of the annealing temperature of titanium dioxide nanoparticles (TiO2 NPs) on luminescent performances of solution-based electrogenerated chemiluminescence (ECL) cells. The TiO2 NPs were spin-coated on a fluorine-doped tin oxide (FTO) cathode as an electron injection layer and then annealed at different temperatures of 250 °C and 450 °C. An orange-red ECL solution was prepared by dissolving a ruthenium complex in propylene carbonate. The ECL cell was fabricated by sandwiching the solution between the FTO anode and the TiO2 NPs-coated FTO cathode and evaluated under direct current (DC) voltages. The 450 °C-annealed cell was found to exhibit significant improvements in the luminance and the lifetime in comparison with the 250 °C-annealed cell.