The main objective of the present study was to isolation and identification of the cause carob leaves spots. In this study, a total of 4 fungal isolates (referred as A1, A2 and A3) were obtained from symptomatic leaves collected from carob trees distribution in El-Beida city and its suburbs. The pathogen associated with the disease was identified as Alternaria alternata (Fr.) Keissl. All the isolates produced olive-brown to medium-brown conidia with obclavate shape, but the isolates varied in size (length) of conidia, the number of cells per conidium, rate of growth and sporulation on media. Koch´s postulate was verified by inoculating healthy leaves. This was the first report of leaf spot disease of carob caused by Alternaria alternata in Libya.