The cruise liner has enhanced emergency power capabilities, new fire technology and new restaurants, including Guy's Burger Joint and the Bluelguana Tequila Bar, Carnival said.
The ship returned to its port of Galveston, Texas, earlier this week and set sail for Mexico Thursday, the company said.
The 2,758-passenger ship was disabled by the February fire in the Gulf of Mexico.
Passengers spent several days without electricity, hot water or working toilets.
The incident led to a review of the company's ships and plans for $700 million in work on the fleet over the next few years, The Miami Herald reported.