Tapioca starch was chemically modified with urea in the presence of borate as crosslinker and catalyst. Fourier transform infrared (FTIR) and viscosity were performed to measure qualitatively the reactivity of the mixture. To improve the hydrophobicity, 10 of lignin (10L) was then added into the starch-urea-borate (SUB) system. The incorporation of lignin leads to lower water uptake film. It was found that lignin retards the urea release and the SUB10L film is stable and stayed intact for one month after immersing in water which shows high potential as a biopolymer for slow release fertilizer. © (2013) Trans Tech Publications, Switzerland.