The victims fell off the upper decks of their floats about an hour apart during a parade Sunday, WWL-TV, New Orleans, reported.
"One person was in stable condition and taken to a local hospital, and the second person was transported from Lee Circle to the trauma center in critical condition," said Ken Bouvier, deputy chief of operations for New Orleans EMS.
The man who initially was in critical condition was upgraded to stable condition Sunday night.
Both men suffered head injuries, EMS officials said.
"In the past, we [have] had people die from falling off floats and going into this second weekend of Mardi Gras, starting Wednesday, we want to send the message to float riders to protect [themselves] and follow their safety rules for riding on floats," Bouvier said.