Forward osmosis (FO) has drawn growing attention in recent years, while the lack of desirable FO membranes has been restricting its further development in industrial applications. In this work, a novel tripodal amine-tris (2-aminoethyl) amine (TAEA), with a dual role of catalyst and reactive amine monomer, is incorporated in the PA selective layer for the first time, to in-situ modify the thin-film composite (TFC) membrane. A series of characterization techniques are employed to investigate the modification mechanism involved, as well as changes in chemical properties and the microstructure of the PA layer in terms of the TAEA content and the amine solution pH. The separation performance and anti-fouling behavior of the TAEA-modified TFC membranes are studied correspondingly. In comparison with the control TFC membrane, modified TFC membranes possess higher water permeability, higher salt rejection, and much lower fouling propensity, and may hold a great potential for FO applications.