Adult onset Still's disease (AOSD) is an uncommon acute systemic inflammatory disease of unknown origin. The clinical features include high spiking fever, arthralgia or arthritis, transient maculopapular rash, lymphadenopathy, hepatosplenomegaly, and serositis. Pericarditis is the most common cardiac manifestation of AOSD and occurs in approximately 30% of cases. A simultaneous occurrence of rapidly progressive bi-valvular regurgitation associated with AOSD has not been previously described. We report a case of a 55-year old woman who underwent mitral valve replacement and Bentall's operation due to acute severe mitral and aortic regurgitation associated with AOSD.