The present work pertains to synthesis of Sm-doped GO/KSrPO 4 (GO/KSrPO 4 : Sm) nanocomposite using ultrasound-assisted method. Successful decoration of graphene oxide sheets with the KSrPO 4 :Sm 3+ phosphor was confirmed using analysis techniques including SEM, EDS, UV/visible spectrometry, XRD, and FTIR of the prepared GO/KSrPO 4 :Sm nanocomposite. Further, photocatalytic activity of this nanocomposite material was studied by examining degradation of methylene blue (MB) dye from water. The effects of several parameters like concentration of Sm 3+ in KSrPO 4 :Sm 3+ phosphor within the GO/KSrPO 4 :Sm nanocomposite photocatalyst, photocatalyst loading, initial dye concentration, pH, and preparation method were evaluated. At a higher concentration of