Herein, we study an optimal control problem of delay differential model to describe the dynamics of tumour-immune interactions in presence of immuno-chemotherapy. The model includes constant delays in the mitotic phase to justify the time required to stim- ulate the effector cells and for the effector cells to develop a suitable response to the tu- mour cells. By applying optimal control theory, we seek to minimize the cost associated with the immuno-chemotherapy and to reduce load of of tumour cells. Non-Negativity of the solutions of the model and existence of an optimal control has also been proven. Optimality conditions and characterization of the control are also discussed. We numeri- cally approximate the solution of the optimal control problem by solving the state system forward and adjoint system backward in time. The numerical simulations show that the combination of immuno-chemotherapy protocol reduces the tumour load in few months of therapy.