In this study design, the PEGylated silver decorated graphene nanocomposites (NGO-AgNPs-PEG) were successfully prepared by eco-friendly non-toxic green synthesis following a novel syn-graphenization method using the aqueous leaf extract of Azadirachta indica (A. indica) (neem) as reducing agent. The prepared Smart pH stimuli responded nanoplatform was thoroughly characterized by various analytical techniques. Since a functional nanocarrier is very essential for cancer therapy, it could quickly guide the loaded anticancer drug to the tumor site to decrease the side effect. In order to overcome the side effects of doxorubicin (DOX), an anticancer drug, it was incorporated into amino PEGylated NGO-AgNPs nanocomposites. Considering drug loading and release studies, it may be concluded that improved drug loading efficiency (218%) and more pH-responsive controlled release (following Korsmeyer–Peppas model release kinetics) of DOX from NGO-AgNPs-PEG lead to a promising nanocarrier for the anticancer drug. The cytotoxicity study results, on HaCaT cell lines, indicated DOX-loaded PEGylated functionalized nanographene oxides, as compared to free DOX, had lesser harmful effect on normal cells than cancer cells. Increased cytotoxicity was exhibited in the cancerous cells (HeLa cell lines) treated with DOX loaded PEGylated silver functionalized nanographene oxide compared to covalently conjugated NGO-DOX. So, the effective delivery and release of the anticancer drug into acidic microenvironment of the targeted tumour cells would bring out higher therapeutic efficacy than pure NGO. Such a gold standard biocompatible PEGylated silver decorated NGO theranostic nanoplatform may be an excellent nano cargo for targeted and controlled drug delivery in cancer therapy. © 2019, Springer Nature Switzerland AG.