Bullock won a best actress Oscar for her performance in the film, which was a hit in the United States and is to debut in England next Tuesday.
UsMagazine.com said Bullock canceled her planned appearance at the premiere in the wake of a tabloid report claiming her reality television star husband, Jesse James, cheated on her with a model.
"Due to unforeseen personal reasons, a trip abroad to support 'The Blind Side' has been deemed impossible at this time. I apologize for any inconvenience this may have caused and thank you for your continued support of the film," said a statement issued by Bullock through Warner Brothers U.K.
UsMagazine.com said neither Bullock nor James has addressed the allegation of infidelity.
The couple have been married for nearly five years.