Aims: This study was conducted to determine the seroprevalence of bovine brucellosis in Al Gadarif state -Eastern Sudan- and to evaluate the sensitivity of RBPT, mRBPT, and milk ring test for serodiagnosis of bovine brucellosis. Study Design: Collect serum and milk samples and apply the recommended tests for diagnosis. Place and Duration of Study: This study was carried out in Al Gadarif state regional laboratory and Central Veterinary Research Laboratory (CVRL) in 2015. Methodology: A total of 367 serum samples were collected from 12 localities which include: Al Fao, Fashaga, Baldiat Al Gadarif, Wasat Gadarif, West Gadarif, Basonda, Al Gorisha, Al rhad,Mafaza , Butana, East Galapat and Gla nahl. Also, 100 bulk milk samples have been collected from Baldiat Al Gadarif, West Gadarif, Wasat Gadarif, and Fashaga and subjected to the milk ring test. All collected sera samples were tested for Brucella antibodies using the following serological tests: Rose Bengal Plate Test (RBPT), modified Rose Bengal Plate test (mRBT 1:2 and 1:3) and, c.ELISA test, the last test was done for 143 serum samples only. Results: The overall seroprevalence was 35.7%, 38.4%, 42.2% and 8.4% using RBPT, mRBPT (1:2), mRBPT (1:3) and c.ELISA tests respectively. According to this study the lowest seroprevalence was observed in Al Fao locality (11.1%), and the highest seroprevalence was in Al Gorisha Locality (71.4%).There was similarity in seroprevalence rate results using RBPT (1:2) and RBPT (1:3) in Al rahd (43.6%), Al Gorisha (85.7%) and Mafaza (50%) localities. Seroprevalence rate showed 10.9% and 9.1% in males and females respectively. There was no association between sex-as risk factor- and cattle brucellosis. Using the milk ring test the overall prevalence of positive milk samples was 39% (39/100). The highest prevalence was in Fashaga (60%), followed by Wasat Gadarif (46.7%). Baldiat Al Gadarif showed the lowest prevalence (22.9%). Conclusion: The serological investigation proved the occurrence of bovine brucellosis in Al Gadarif state -Eastern Sudan - using the recommended tests.