Cephaleuros virescens is a plant parasitic green alga, causing several diseases on guava such as leaf spot, fruit spot and branches canker as well as defoliation and twigs die-back in tropical and subtropical countries. During the growing season of 2012-2013, examination of guava (Psidium guajava L.) trees growing in orchards and nurseries at Qalubyia and Giza Governorates revealed that several trees were observed with symptoms and signs of fruit and leaf spots as well as branch canker diseases (Fig. 1). Symptoms on leaves and fruits often observed as roughly circular spots with irregular borders in reddish brown to reddish purple or rust brown with reddish margin, crowded or scattered, especially in the early stages. Spots on guava leaves were observed as intercellular, full-thickness necrosis, destroying both upper and lower epidermal cell layers and all intervening, tissue discoloration beneath the bark. The presence of an orange velvet-like growth (sporangiophores and sporangia) of the pathogen was also observed. Zoospores were released when sporangia placed in water drops. The causal pathogen was isolated from guava infected tissues, purified and identified as Cephaleuros virescens.