The Modern Family star was amongst the stars set to walk the red carpet of the awards ceremony taking place Sunday night (February 24) in Los Angeles.
According to the Daily Mail, the actress is currently in hospital for an operation.
A source close to Vergara has said: "Sofia is fine and there is nothing to worry about."
The star's reps have yet to reveal the nature of her condition.
Kristen Stewart, Jennifer Garner, and Jane Fonda are among the celebrities set to present at the Oscars this year.
Photo gallery - Oscar nominees in pictures: