Background: Dengue and chikungunya are mosquito-borne viral diseases of major global health concern. In Tanzania, information on risk factors for dengue and chikungunya is limited. We investigated individual, household, socioeconomic , demographic and environmental risk factors for dengue and chikungunya seropositivity. Methods: A cross sectional study was undertaken which included a total of 1003 participants from NorthEastern Tanzania, to determine the sero-prevalence of dengue and chikungunya and to investigate associated risk factors. Logistic regression models were used to determine the risk factors for dengue and chikungunya seropositivity. Results: Environmental factors such as living in a house with uncovered containers within the compound had higher odds of being chikungunya IgM seropositive (OR Z 2.89; 95% CI: 1.76 e4.76). Also, participants who kept hoofed animals in their home and who lived in a house