Pristine AgNbO3 and La-doped AgNbO3 perovskite as photocatalysts were successfully synthesized using the solid state method. The synthesized photocatalysts were then characterized by utilising various analytical techniques. The structural characterizations confirmed that the samples are crystalline in nature and without the presence of any secondary phase. The expansion of unit cell parameters from XRD analysis confirmed the inclusion of La into the AgNbO3 lattice structure. FESEM studies revealed irregular morphology of pristine AgNbO3 with the average particle size of 1.42 μm. The particle size decreased as the amount of La increased, with the 10% La-doped AgNbO3 showing the smallest particle size at 0.71 μm. FESEM-EDX confirmed the presence of Ag, Nb, and La atoms. The photocatalytic efficiency of the pristine AgNbO3 and La-doped AgNbO3 were evaluated by performing the photocatalytic degradation of Rhodamine B and methylene blue dyes. The results indicated that La-doping has improved the photocatalytic efficiency of AgNbO3. The increase in efficiency of La-doped AgNbO3 could be attributed to the reduction in particle size and the increased amount of electron–hole pairs being generated during photocatalysis.