The Raman active modes of CuAlS2 have been investigated at ambient temperature under high pressure using nitrogen gas as pressure transmitting medium up to 16.3 GPa. An assignment of the symmetry of the zone-centered modes is proposed on the basis of their pressure dependence as compared to that of the corresponding modes in the zincblende structure (ZnS). In this sense, a schematic representation of the cubic Brillouin zone showing its high symmetry points and the correlation with the CuAlS2 chalcopyrite lattice modes is presented. The high pressure effect on the phonon frequencies is discussed in terms of the Grïneisen parameters. A structural first-order phase transition was observed at about 16.3 GPa. After a pressure cycle was completed, the Raman scattering measurements performed on the retrieved samples gave some information about the size of the crystallites created by the phase transition.