Elastomer has been used as an engineering component in various fields and in some particular cases, the material is exposed to aggressive solvents such as biodiesel during the service. The study of the durability of elastomer in the presence of biodiesel is essential, especially when biodiesel has its potential in substituting the conventional diesel in the future. The present paper investigates the effect of swelling level on the mechanical response of swollen rubbers by palm biodiesel, under fatigue loading. Two swelling levels are considered. The fatigue tests are conducted on both dry and swollen rubbers at various maximum stretch values and a constant zero loading ratio. FESEM analysis is carried out to investigate the physical fatigue damage mechanism induced in the swollen rubber. The fatigue lifetimecurves revealed that swollen rubbers have a shorter lifetime compared to the dry ones. However, the swelling level might induce an effect when the crack nucleates up to a certain size, which is 1 mm for our case. FESEM results showed that the swelling level has no effect on the morphology of crack nucleation and propagation, regardless of the loading condition.