Madonna was caught voicing her disgust after receiving a hydrangea before a press conference at the Venice Film Festival.
"I absolutely loathe hydrangeas," Madonna said to the person next to her, adding, "He obviously doesn't know that."
Madonna accepted the flower and quickly put it under the table, while making a face at her friend.
The 53-year-old singer apparently did not realize that her microphone was on as she made the ungracious comment.
Madonna was in Venice to promote her upcoming film "W.E.," which she wrote and directed. The film stars Abbie Cornish, Andrea Riseborough and James D'Arcy and is slated for release on December 9, 2011.
During the Festival, Madonna also announced that she is working on her 12th studio recording, which she plans to debut in spring 2012.
Madonna's new album will be the first since entering her $120 million deal with Live Nation in 2007, after leaving the Maverick label she started with Time Warner. The singer's last record for her former label and last album of original recordings was 2008's "Hard Candy."
Madonna's ex-husband, director Guy Ritchie welcomed a son on Monday with his girlfriend Jacqui Ainsley.
Last month, the singer celebrated her 53rd birthday with a romantic getaway with 24-year-old French break dancer Brahim Zaibat.
Zaibat recently opened up about meeting the singer, telling the British newspaper the Daily Mail, "It wasn't like meeting a monster! She's just a woman like all the others. She's an extraordinary artist and world famous, of course, but a woman above all."
The pop star, who officially turned 53 on Tuesday, August 16, has been linked to Zaibat since last year, after he performed at the launch of Madonna's clothing line at Macy's in New York, following her split from Brazilian model Jesus Luz, who is also 24.
Watch Madonna's hydrangea moment below.