This study investigated mammalian involvement in an outbreak of bubonic plague in Mbulu District, northern Tanzania, in March 2007. Plague is a rodent-borne zoo- notic disease that spreads to humans through fleas infected with Yersinia pestis. Live trapping of rodents and shrews was conducted in fallow and crop fields, peri- domestic areas, houses and the neighboring forest reserve. Serum was separated from blood of captured animals. A rapid diagnostic test (RDT) was used for diag- nosis of plague infection. An ELISA technique was used to detect antibodies against Yersinia pestis fraction 1 antigen. Wild and commensal rodents tested positive by RDT, indicating current infection in clinically healthy ani- mals. The ELISA showed that wild rodents (Lophuromys flavopunctatus, Praomys delectorum, Graphiurus muri- nus, Lemniscomys striatus) and commensal rats (Rattus rattus, Mastomys natalensis, Mus minutoides) were Y. pestis-positive. Two potential vectors, Xenopsylla brasi- liensis and Dinopsyllus lypusus, were found on wild and commensal rodents with a flea index of 1.8. We conclude that diverse potential mammalian reservoirs and efficient vectors of Y. pestis are present in abundance in Dongo- besh and could lead to persistence and future plague outbreaks.