Metal–organic frameworks (MOFs) have low conductivity, which is not conducive to further application. To address the issue, in this work, using carboxylation multiwall carbon nanotubes (MWCNTs-COOH) as carbon materials, benzene-1,4-dicarboxylic acid (PTA) as organic ligands, nickel nitrate hexahydrate (Ni(NO3)2·6H2O) as transition metal ions precursors, MWCNTs decorated with nickel MOFs (Ni-MOFs/MWCNTs) nanohybrids were fabricated via in situ growth by a one-pot solvothermal method. The electrochemical properties of the Ni-MOFs/MWCNTs nanohybrids obtained by adjusting the dosage of MWCNTs-COOH and the experimental conditions as electrode materials for supercapacitors (SCs) were investigated. The results showed that the Ni-MOFs nanoflowers self-assembled by nanorods were in situ growth on the MWCNTs, which could avoid the agglomeration of Ni-MOFs and MWCNTs, enhance the specific surface area, and expose more active sites to improve the electrochemical properties. The specific capacity of the Ni-MOFs/MWCNTs nanohybrids as electrode materials obtained at the optimal experimental conditions was 749.6 C g−1 at 1.0 A g−1.