The Ugly Betty star has been in tough rehearsals to play sexy showgirl Roxie Hart in the London production but fell ill just before opening night.
But Ferrera remained professional and took to the stage for the crowd at the Garrick Theatre.
Speaking with a strained voice on British TV show This Morning on Tuesday (08Nov11), she says, "I was a little under the weather but I had an amazing time. It was so much fun and just great to have an audience and be on stage and get to share. Last night was definitely a dream come true."
During the interview, Ferrera was surprised with a video message from her Ugly Betty co-star Ashley Jensen wishing her luck for her turn in Chicago, and Ferrera exclaimed, "Thank you Ashley! I love Ashley so much."