Epitaxial BiVO<sub>4</sub> photoanodes with precisely controlled crystallographic orientations were fabricated to elucidate the intrinsic influence of facet anisotropy on photoelectrochemical (PEC) glycerol oxidation. The <i>b</i>-axis-oriented (0<i>k</i>0) BiVO<sub>4</sub> film exhibited a 2.4-fold higher photocurrent density and a 2.6-fold greater charge-separation efficiency than the <i>c</i>-axis-oriented (00<i>l</i>) film, achieving a production rate of 81.4 mmol m<sup>-2</sup> h<sup>-1</sup> under AM 1.5 G illumination. PEC and charge-transfer analyses reveal that the enhanced activity of the (0<i>k</i>0) facet originates primarily from improved bulk charge separation and transport rather than surface catalytic effects. This work establishes crystallographic orientation control as an effective design strategy for developing energy-efficient oxide photoanodes for solar-driven glycerol oxidation beyond conventional water splitting.