In this paper we present the results of phytolith investigations at two archaeological sites in northwestern Morocco: Khil (Tangier) and Kaf Taht el-Ghar (T´etouan). The two sites located in Western Maghreb, one on the Atlantic and one on the Mediterranean coast, were investigated in the framework of the AGRIWESTMED project. Phytolith analysis complemented archaeobotanical, geoarchaeological and archaeological investigations to better identify plant use during the entire occupation sequence. At Khil 16 samples have been studied, coming from two profiles excavated in two different caves of the same system - grotte B and grotte C - that span a chronology comprised between the early Neolithic and the historic period. At Kaf Taht el-Ghar, 15 samples were analysed spanning from the Palaeolithic to the Historic period. Results show that at Khil plants are widely used from the very beginning of the Early Neolithic sequence. The surrounding vegetation was exploited and both C3 and C4 grasses were used, inside the cave. At the same time a wide array of other plants was utilised, such as palms and woody taxa. Phytolith analysis at the site of Kaf Taht el-Ghar indicates that crop processing was most probably not taking place on site. However, the predominance in the samples of C3 grasses morphologies agrees with the finding of previous macro botanical studies that identified cultivated wheat and barley in this cave deposits. A very interesting aspect of the phytolith assemblages of Kaf Taht el-Ghar is the widespread use of palm leaves and their gradual disappearance through time that coincides with an increase in the use of woody species.