Biodiesel is a methyl or ethyl fatty acid esters formed by transesterifying vegetable oils (both edible and non edible) or animal fats. In this research, biodiesel is produced by in-situ transesterification (direct transesterification) method from the seeds of rubber tree using KOH as a catalyst. The influence of methanol to seeds ratio, reaction time, temperature and catalyst concentration was investigated. Important properties of biodiesel such as free fatty acid(FFA), viscosity, pour point, density etc were also investigated. The result shows that the best ratio of seeds to methanol was 1:6 (10 g seedswith 60 g methanol), 120 minutes reaction time at 60 degree celcius reaction temperature and catalyst concentration of 2.5 g. The maximum yield obtain was 74.5;. This study supports the production of biodiesel from the rubber seeds using direct transesteterification method from the seeds as an alternative to diesel fuel.