The present study focuses on the development of a chitosan functionalized nanobiocomposite for the co-delivery of two anti-cancer drugs camptothecin (CPT) and 3,3′‑Diindolylmethane (DIM). The difference in the mechanism of action of the two drugs makes them a promising candidate to produce a synergistic effect against breast cancer. Herein a nanobiocomposite was developed by functionalizing a natural polymer chitosan to graphene oxide nanoparticles and decorated with folic acid. The nanobiocomposite thus synthesized was loaded with camptothecin and 3,3′‑Diindolylmethane and characterized by X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible spectroscopy (UV) and atomic force microscopy (AFM).Biocompatibility was assayed by hemolysis and anti-inflammatory assay. The cellular toxicity was measured by 3‑(4,5‑Dimethylthiazol‑2‑yl)‑2,5‑Diphenyltetrazolium Bromide (MTT), Sulforhodamine B (SRB) and cell death assay against MCF-7 cell lines. Further in vivo studies were carried out to analyze the biodistribution of the drug, blood biochemical analysis and bioavailability of the drug. The data revealed a significant increase in anticancer activity after co-loading of CPT and DIM to the nanocarrier. Also in-vivo studies revealed that DIM successfully masked the toxic effects produced by CPT. © 2018 Elsevier B.V.