The mechanical behaviour of metal matrix composites (MMCs) under dynamic loading is commonly improved by surface treatments like cold-rolling or shot-peening. In this paper, we focus on a new mechanical surface treatment: ultrasonic shot-peening. Residual stresses generated by ultrasonic and conventional shot-peening in an aluminium matrix alloy (Al 7075) reinforced with 27 vol.% SIC whiskers are investigated. To this end, three complementary techniques are used. On the one hand, the X-ray and neutron diffraction methods allow surface and in depth measurements respectively and give information on both the matrix and the reinforcement residual stress field. On the other hand, the step by step hole drilling method is applied to study the macroscopic residual stress gradient generated in the MMC. The aim of this work is to compare the residual stress gradients induced by ultrasonic and conventional shot-peening in an aluminium MMC and to conclude if the ultrasonic shot-peening process can lead to the same order of prestressed thickness than conventional shot-peening.