Severe outbreak of anthracnose diseases caused by Colletotrichum gloesporioides f.sp. manihotis on cassava (Manihot esculenta Crantz) occured in north-western Tanzania in October, 2011. Thirteen cassava leaf samples with disease symptoms were collected from Maruku Agricultural Research Institute (MARI) and from farmers. The collected sam-ples were tested for infection using Blotter method. The results indicated that, all 13 leaf samples (100%) were infected by C. gloesporioides f.sp. manihotis. Three isolates of the fungus per sample were sub-cultured on Potato Dextrose Agar (PDA) for seven days then each isolate was sprayed-inoculated onto 4-week-old sprouting leaves of cassava cut-tings, var Mkombozi grown in pots in the screenhouse maintained at 27°C and relative humidity of 85% - 90%. All iso-lates were pathogenic on cassava and produced similar symptoms as those observed under field conditions. This is the first report of C. gloesporioides f.sp. manihotis a causal agent of anthracnose disease of cassava in Tanzania.