Abstract: Corky root rot symptoms caused by Pyrenochaeta lycopersici were observed on roots and stem bases of tomato plants under plastic houses in Jordan. Symptoms included chlorosis of foliage, stunting, root necrosis and poor fruit setting. The isolated fungus from diseased tomato plants formed a gray to dark green mycelium on PDA media with hyaline, uni-cellular cylindrical conidia. The main stem of diseased plants appeared to have cracked lesions along the length of the root with corky appearance. Based on the disease symptoms and morphological characteristics of the isolated fungus and pathogenicity test, Pyrenochaeta lycopersici was identified as the causal agent of the disease. This study seems to be the first study of corky root rot of tomato caused by Pyrenochaeta lycopersici in Jordan.