Among typical energy storage devices, supercapacitors play a predominant role in industry and our life owing to their rapid charge/discharge rate, superior lifespan, high power density, low cost, and outstanding safety. However, their low energy density has severely hindered their further development. For active electrode materials, graphene-based mesoporous nanosheets (GMNs) can combine the advantages from graphene and mesoporous materials, which can be applied to significantly enhance the energy density of supercapacitors. Here, we review the recent advances in GMNs for supercapacitors, focusing on in-plane mesoporous graphene and sandwich-like graphene-based heterostructures. Firstly, the synthesis of in-plane mesoporous graphene with ordered and disordered mesopores for supercapacitors is introduced. Secondly, sandwich-like graphene-based heterostructures are classified into mesoporous carbon/graphene, mesoporous heteroatom-doped carbon/graphene, mesoporous conducting polymer/graphene, and mesoporous metal oxide/graphene, and their applications in supercapacitors are discussed in detail. Finally, the challenges and opportunities of GMNs for high-performance supercapacitors are proposed.