Synthesis of silver nanoparticle using Gambier leaves (Uncaria gambier Roxb) extract and diethanol amine (DEA) as stabilizer has been done successfully. Synthesis process was prepared by using the hydrothermal method. The results were characterized using UV-Vis, XRD and TEM. UV-Vis analysis showed that DEA as stabilizer has effective to control of stability and production of silver nanoparticle colloid. XRD analysis demonstrated peaks of silver which was suitable with the standard peaks of silver. TEM images conformed that synthesis using this method produced very fine particle with particles size of around 25 nm.