Background: It is estimated that 13% of the 35 million People Living with HIV (PLWHIV) globally, are those aged ≥ 50 years. The objective of this study was to determine the prevalence and risk factors for HIV among adult aged 50 years and above in Rombo district, northern Tanzania. Methods: A cross sectional study was conducted from April to June 2015 among older adults aged 50 years and above in Rombo district. Multistage sampling technique was used to get the participants. Questionnaires were used to collect key information during face to face interviews. Interviews were followed by blood sample collection for HIV diagnosis. Pre and post test HIV counseling was done individually for each participant. Data was entered and analyzed using Statistical Package for Social Science (SPSS). Results: A total of 600 people were enrolled. Their age ranged from 50 to 90 years with mean of 64.9 (±SD 10.3) years. The HIV prevalence was 1.7% (n=10). Prevalence was higher in women 2.1% compared to men 1.3%. Sixty percent (n=350) were knowledgeable on HIV transmission and only 40% (n=216) were knowledgeable on HIV prevention. Age of partner< 50 years, condom use, poor knowledge on HIV prevention and perception of risk on HIV were significantly associated with HIV in univariate analysis, but only partner’s age of <50 years remained significantly after controlling for confounders. Conclusion: HIV prevalence among older adults in this rural population was low. Despite low prevalence, overall knowledge on HIV transmission and prevention was low in this age group. There is a need for strategies to improve HIV preventive knowledge and testing in this group in order to continue keeping the transmission at low levels. Key words: Older adults, HIV, prevalence, risk factors, Tanzania