A DISSERTATION SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN PUBLIC HEALTH AND FOOD SAFETY OF SOKOINE UNIVERSITYOF AGRICULTURE, MOROGORO, TANZANIA.A cross-sectional study was conducted between November,2014 and March,2015 in Lushoto and Rungwe districts of Mbeya and Tanga regions respectively to estimate the seroprevalenceof bovine brucellosis in smallholder dairy cattle and the associated risk factors. Blood samples from 400 animals from Lushoto (n=172)and Rungwe (n=228) were tested for Brucella circulating antibodies using Rose Bengal Plate Test (RBPT), Lateral Flow Assay (LFA) and Competitive-enzyme-Linked Immunosorbent Assay (cELISA).Information regarding risk factors associated with Brucella seropositivity, smallholder farmers’ knowledge, attitudes and practices (KAPs) were collected using structured questionnairesadministered to 400 smallholder households.All animals tested negative on RBPT and LFA tests, while the overall seroprevalence based on cELISA results,was 5.3%.Seropositivity was significantly higher in Rungwe (8.3%) than Lushoto (1.2%) (p=0.01).Although femaleshad higher seropositivity (5.8%)compared to males (2.7%), the difference was not statistically significance (p=0.28). Furthermore, risk of seropositivity was not associated to breeding method(Artificial Insemination or bull service), history of abortion herd size, vaccination against brucellosisand number of services before last conception. District (Rungwe) (OR=6.49, CI=1.46-28.76, p=0.01) was a significant risk factor that was associated with brucellosis seropositivity. Results further revealed that majority of farmers had poor knowledge and awareness of brucellosis and their practices are potential risk factors for disease transmission.Bovine brucellosis is prevalent in the study area; this calls for public health awareness programmes, and implementation of strict control measures to curb further spread of the disease in the smallholder production systems within and outside the study area.