Abstract: Au–Pd NPs@CNSs/GO nanocomposites have been fabricated by the in situ growth of Au–Pd nanoparticles on carbon nanospheres (CNSs) using ascorbic acid as reducing agent and diethylenetriamine (DETA) as a coupling linker and the subsequent assembly of the Au–Pd NPs@CNSs on graphene oxide (GO). In the nanocomposites, the Au–Pd NPs alloys have an average particle diameter of less than 10 nm. The nanocomposites show excellent catalytic activity for methylene blue with a high degradation efficiency above 99% in the presence of NaBH4 in aqueous solution, which is attributed to the effects of Au–Pd NPs alloys in the nanocomposites. In addition, the catalyst exhibits good selectivity for methylene blue in the presence of other organic dyes. Meanwhile, the catalytic activity remains unchanged for nine cycles. Such features ensure a very promising application of nanocomposites in the selective degradation of methylene blue in dyes mixtures. © 2020, Pleiades Publishing, Ltd.