The field of photocatalysis is an active area owing to the possible contributions to solve some challenging problems such as sustainable energy production, environmental pollution control, and even global warming. Unfortunately, traditional photocatalysts, especially semiconductors, suffer from inherent deficiencies, which include high activation barriers, the low mobility of charge carriers, and poor long-term stabilities. Herein, we demonstrate a plasmonic photocatalyst based on unidirectional gold nanorod arrays fabricated by using the oblique-angle deposition (OAD) technique. The fabricated gold nanorod arrays exhibit a remarkable plasmonic anisotropy, which depends on the direction of the incoming light. By employing these arrays as a plasmonic catalyst, a clear improvement and control in the catalytic reduction of o-nitroaniline to 1,2-benzenediamine, depending on the directionalities and anisotropic plasmonic properties of the gold nanorods, was obtained. These results suggest that such unique characteristics of directional gold nanorod arrays could greatly impact several technological areas, not only in plasmon-enhanced photocatalysis but in biosensing and optofluidic applications.