Amino silane magnetic nanocomposite decorated on graphene oxide (GO-Fe3O4-APTES) was successfully prepared by organic transformation reaction followed by co-precipitation method. The nanocomposite was characterised by using FT-IR, XRD, FE-SEM, TEM, EDS mapping, VSM, Raman spectroscopy, BET surface area analyzer, Zeta potential and UV-visible spectrophotometer. From TEM results we observed that 8 nm sized particles successfully modified on GO surface. The surface area of GO-Fe3O4-APTES was 57.9 m2 g−1. The magnetic Saturation value of GO-Fe3O4-APTES was 30.6 emu g−1 and the S-like magnetization of all the samples shows super paramagnetic in nature. Due to magnetic nature adsorbent, it could be easily separated from aqueous solution. GO-Fe3O4-APTES material was highly selective for Chromium (VI) removal from aqueous solution. About 91% of Chromium (VI) was removed at pH 3, 160 rpm of shaking speed, 0.3 g l−1 of adsorbent dose and 10 h of contact time. The adsorption process of Chromium (VI) on GO-Fe3O4-APTES follows Pseudo-second-order kinetic and Langmuir isotherm model because of high coefficient of determination value (R2 = 0.99). The maximum adsorption capacity (q m ) of GO-Fe3O4- APTES was observed at 60.53 mg g−1. The synthesized material was desorbed with 0.5 M NaOH and recycled up to five cycles. After five cycles, the removal efficiency of Chromium (VI) possesses high efficacy towards GO-Fe3O4-APTES. Mechanistically, adsorption of Chromium (VI) follows strong electrostatic attraction between adsorbate and adsorbent. GO-Fe3O4-APTES has potential adsorbent for the adsorption of Chromium (VI) in waste water treatment. Furthermore, the GO-Fe3O4-APTES were tested for antibacterial properties against gram negative (Escherichia coli) and gram positive (Bacillus subtilis) bacterial strain. The synthesized material responds positively towards antibacterial activity.