ABSTRACT. – The grazing on the invasive Caulerpa racemosa var. cylindracea (Sonder) Verlaque, Huisman et Boudouresque has been studied in the Gulf of Marseilles. After three years of field observations, we have determined that the grazing began at the end of summer and increased in autumn when the extent of C. racemosa meadows was at a maximum. The Mediterranean herbivorous fish, Boops boops and Sarpa salpa, essentially grazed on Caulerpa racemosa in late summer and early autumn. The regular sea urchins Paracentrotus lividus and Sphaerechinus granularis also consumed C. racemosa. The feeding behaviour of S. granularis was generalist with 31.2% ± 2.9 of C. racemosa in gut contents. The consumption of C. racemosa by the more selective sea urchin P. lividus was lower (9.8% ± 2.5 of C. racemosa in gut contents). Grazing activity was very limited in space and in time (end of summer and autumn) and quickly compensated by the enhancement of the stolon ramification of C. racemosa, so the consumers identified at Marseilles do not seem able to limit the spread of this introduced species.