The clean-up of viscous crude-oil spills is a global challenge. Hydrophobic and oleophilic oil sorbents have been demonstrated as promising candidates for oil-spill remediation. However, the sorption speeds of these oil sorbents for viscous crude oil are rather limited. Herein we report a Joule-heated graphene-wrapped sponge (GWS) to clean-up viscous crude oil at a high sorption speed. The Joule heat of the GWS reduced in situ the viscosity of the crude oil, which prominently increased the oil-diffusion coefficient in the pores of the GWS and thus speeded up the oil-sorption rate. The oil-sorption time was reduced by 94.6% compared with that of non-heated GWS. Besides, the oil-recovery speed was increased because of the viscosity decrease of crude oil. This in situ Joule self-heated sorbent design will promote the practical application of hydrophobic and oleophilic oil sorbents in the clean-up of viscous crude-oil spills.