"I used to work on a cruise ship, a long time ago," said Hudson before performing at a Carnival news conference in midtown Manhattan. "That's what I did before I did 'American Idol.'"
Her stint aboard a Disney cruise ship was "my test," she said. "Two days later, I went in and auditioned for 'American Idol.'"
Headlining the Carnival series "is like a full circle," she added.
Hudson is scheduled to perform June 18 on Carnival Ecstasy and June 19 on Carnival Breeze, both in Cozumel, Mexico.
Carnival has struggled to restore its image after three ships broke down last year. Images of passengers stranded at sea, ships towed back to port and trip cancellations created a torrent of bad publicity for the company that depressed ticket prices and revenue.
Other performers and bands scheduled to perform are Chicago, Daughtry, Foreigner, Gavin DeGraw, Jewel, Kansas, Lady Antebellum, LeAnn Rimes, Martina McBride, Olivia Newton-John, REO Speedwagon, STYX and Trace Adkins.
So far 49 shows are confirmed for the year. Styx will kick off the series with an April 7 show on the Fantasy in Nassau. In all, eight ships are participating.
Tickets will only be sold to individuals taking the cruise.
Hudson sang "One Night Only" and several other songs for about 200 people at the Cutting Room, a Manhattan performance space, where Carnival's senior vice president of guest operations, Mark Tamis, announced the program.