The orientational dynamics in the isotropic phase of a comb-like nematic polymer with mesogenic and functional side groups is studied using the Kerr effect and dielectric spectroscopy methods. For the first time, it has been found that, in contrast to low-molecular-weight mesogens, the relaxation of the electric birefringence of a melt above the temperature of the nematic–isotropic phase transition in a mesogenic polymer can be represented by a sum of several exponential processes, two of which play a decisive role. These processes replace each other in the temperature range of about 50°C. Dielectric spectroscopy also makes it possible to distinguish two orientational relaxation processes, one of which is due to the rotation of the side mesogenic groups, and the second is associated with the motion of the main chain segments.