Pressure retarded osmosis (PRO) has been identified as a promising technology to harvest the salinity gradient energy. For practical applications of PRO process, membrane fouling is a challenging issue as it leads to severe decline of PRO performance in terms of water flux and power density. It is imperative to develop anti-fouling membranes for PRO process. The current study demonstrated the unique roles and the great potential of aminosilane in developing anti-fouling thin film composite (TFC) PRO membranes. Experimental results revealed that aminosilane as a grafting agent can modify both the support layer (interior) and the selective layer of PRO membranes with remarkably enhanced hydrophilicity via a very simple grafting procedure. In the grafting, aminosilane was able to minimize the pore-blocking issue with almost no increase in the membrane structural parameter (S). Meanwhile, the membrane mechanical strength was well maintained with the grafting due to the capability of aminosilane as a cross-linker. With enhanced hydrophilicity, it was interestingly found that the water permeability (A) was doubled, while the salt rejection was maintained nearly unchanged. The combination of these effects brought in remarkably enhanced water flux, power density and anti-fouling property to the resultant membrane.