The microscopic origin of the near-band-edge emission in low-temperature aqueous chemicallygrown ZnO nanorods is analyzed. For the as-grown nanorods, a broad and almost featureless main emission band at 3.366 eV is observed due the presence of a high donor and defect density. After the nanorods have been annealed at 800 °C for 1 hour in an oxygen atmosphere, a remarkable reduction of the linewidth of the near-band-edge emission from 10 meV to 4 meV is observed. Sharp and distinguishable excitonic transitions are visible. Time-resolved photoluminescence measurements show very fast recombination times of 11 ps for the as-grown sample while the radiative recombination time increases to 80 ps after the sample is annealed in oxygen atmosphere.