Sm3+-doped g-C3N4 nanosheets with efficient solar photocatalytic activity were synthesized and their structural and optical properties were characterized. UV-vis diffuse reflectance spectral studies revealed that the absorption edge is red shifted in all Sm3+-doped samples and Sm3+-doping decreases the band gap of g-C3N4, thereby increases visible light absorption. The separation efficiency of the electrons and holes was obtained from PL spectral studies. The solar photocatalytic activity of the synthesized catalysts was assessed by studying the degradation of different dyes under sunlight. The synthesized photocatalyst was applied for the degradation of a synthetic dye effluent and an endocrine disrupting organic compound, salicylic acid under sunlight and showed more efficiency than the commercial photocatalyst, Degussa P-25. Studies revealed that hydroxyl radicals and holes play significant role in the degradation of dye effluent under sunlight. Further, the possible mechanism of the photocatalytic degradation of pollutants using Sm3+-doped graphitic carbon nitride is also proposed.