Graphene aerogel with three-dimensional (3D) interconnected porous structure and good hydrophobicity has been extensively investigated for sorbent materials for oils and demonstrated to be effective. Herein, a 3D polyimide–graphene aerogel (PI-GA) nanocomposite has been prepared by introducing water-soluble polyimide (PI). Benefiting from the synergetic effect of PI and GA, the PI-GA nanocomposite exhibits ultralow density, excellent compressibility and hydrophobicity. When evaluated as a sorbent material for oils and organic solvent, PI-GA nanocomposite has high absorption capacity and can separate oil from water rapidly and efficiently. Furthermore, the mechanical squeezing process can be used for the recycling of the PI-GA due to its excellent compressibility. The excellent absorption performance and robust mechanical properties make the PI-GA suitable for oil cleanup and chemical leakage.