Monoclinic and hexagonal LaPO₄ nanorods were prepared through hydrothermal method without the assistance of additives. The products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). Monoclinic and hexagonal LaPO₄ nanorods can be achieved by adjusting the hydrothermal temperature and the pH value. The photocatalytic activity of monoclinic and hexagonal LaPO₄ nanorods on rhodamine B (RB) and Congo red (CR) under UV irradiation was investigated, respectively. Interestingly, the monoclinic and hexagonal phase shows different photocatalytic performance for the photodegradation of the organic RB and CR dye.