This study is the first to report the occurrence and distribution of both Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) in Rwanda. Eight major cassava-growing districts in the country were surveyed to determine the distribution and variability of symptom phenotypes associated with cassava brown streak disease, and the genetic diversity of cassava brown streak viruses. Phylogenetic analysis and the estimates of evolutionary divergence, using partial sequences of the coat protein gene, revealed that in Rwanda there is one type of CBSV and an indication of diverse UCBSV.