The less investigated Bi layer-structured oxides, Na0.5Bi2.5Nb2O9, have been explored in this work. Its distinctive layered structure induces internal electric field, which is advantageous for charge separation and transfer. As a result, the compound is an effective photocatalyst. Such a property can be further enhanced by tuning the morphology. Although all samples show similar crystal structures and optical properties, a hydrothermal technique results in unique thin nanosheets while a microwave-assisted hydrothermal and a molten-salt technique yield irregular-shape nanoparticles and orthorhombic-shape microparticles, respectively. Among all samples, nanosheets exhibit the best Rhodamine B photodegradation. The outstanding performance is attributed to the nanosheet feature, which facilitates charge separation, and the highly exposed reactive {001} facet. Furthermore, the high efficiency, stability, and recyclability suggest it to be a potential candidate for other photocatalytic reactions and similar strategies could be used to design photocatalysts for green and sustainable solutions to environmental problems.