We have investigated the structural and electronic properties of CoSi2 by using a generalized gradient approximation of the density functional theory and ab initio pseudopotentials. The calculated lattice constant and electronic band structure have been used in the application of a linear response approach based on density functional perturbation theory for phonon studies. The structural results are in good agreement with previous works. The calculated phonon spectra are in good agreement with available experimental data. A detailed discussion of atomic displacement pattern is provided corresponding to the two sets of LO and TO phonon modes.