Ultrathin two-dimensional (2D) metal-organic framework (MOF) nanosheets have been regarded as very promising electrocatalysts, although more efforts need to be devoted to improve their electrocatalytic activity. Here, we have developed ultrathin 2D nanosheet-assembled [Ni3(OH)2(PTA)2(H2O)4]·2H2O (Ni-MOF, PTA = p-benzenedicarboxylic acid) hierarchical flowers, which demonstrate superior electrocatalytic activity and excellent stability for the glucose oxidation reaction (GOR). The ultrathin 2D nanosheet-assembled flower-like nanostructure can provide interconnected open pores, accounting for its high electrocatalytic performance. Additionally, most of the ultrathin 2D nanosheets are in close contact with each other, making the ultrathin 2D nanosheets more stable. Furthermore, the electrocatalytic activity of the Ni-MOF flowers can be adjusted by doping Zn into the framework.