Organisers have pulled his tickets and demanded assurance that he won’t pull any stunts before they return them.
The 40-year-old Bruno and Borat star appears in Martin Scorcese’s highly-nominated film Hugo, playing Station Inspector Gustave.
It was rumoured that Cohen, who is known for his pranks, would turn up dressed as his character in The Dictator, which he is currently filming.
Academy organisers said: “We haven’t banned him, we’re just waiting to hear what he’s going to do.”
A spokesman also added that Cohen was still welcome to attend, but it wasn’t “appropriate” for him to use the Oscars to plug his new movie.
The spokesman said: “We would hope that every studio knows that this is a bad idea. The Red Carpet is not about stunting.”
A source said: “Unless they’re assured that nothing entertaining is going to happen on the Red Carpet, the Academy is not admitting Sacha Baron Cohen to the show.”
To promote Bruno, Cohen arrived at the MTV Movie Awards dressed as the character, flying through the air and landing with his crotch in Eminem’s face.