We study the axial-vector form factor of the nucleons in a constant and homogenous isospin chemical potential using holographic QCD. Nucleon mass splitting in such an isospin medium is taken into account. According to AdS/CFT correspondence, the critical value of the isospin chemical potential equals to UV- boundary value of the time component of the bulk gauge field. We calculate the axial-vector form factor of the proton and neutron in such background in the framework of the hard-wall model and plot the form factors for the isospin chemical potential critical value.