Light-trapping patterns were constructed in TiO2 photoelectrodes for dye-sensitized solar cells (DSSCs) by a one-step femtosecond laser structuring method that utilized ablation to create patterns at the surface of nanostructured TiO2 films. As a result, much more light was trapped in the photoelectrodes. Grating and orthogonal-grid patterns were studied, and the light trapping performance was optimized through the adjustment of pattern spacing, which was easily realized in the laser ablation process. With a 5-μm-spacing orthogonal-grid pattern, DSSCs showed a highest photon-to-electron conversion efficiency of 9.32% under AM 1.5G, a 13.5% improvement compared to the same cell without laser ablation. This simple and universal laser ablation method could be used to process many kinds of nanomaterials, and could be applied for various devices with nanostructures.