The 22-year-old man and 20-year-old woman fell 50 to 60 feet from a cabin balcony, said Julie Benson, spokeswoman for Princess Cruises.
She said the cruise line did not know how they fell overboard, although it appears to have been an accident. Their ship, Princess Cruise's Grand Princess, was about 150 miles off the coast of Galveston, Texas, at the time.
The captain turned the ship around after friends of the man and woman notified the crew at about 1:30 a.m. CDT that they had gone overboard, Benson said. The ship's crew used high-powered spotlights and rescue boats in the search. One passenger was rescued by the ship's boats at 5:30 a.m. and the other at 6 a.m., according to a statement by the cruise line.
The search was aided by the Coast Guard, said Lt. j.g. Jillian Lamb at the District 8 Command Center. A nearby cruise ship also offered assistance, she said.
The man and woman, whom the cruise line declined to name, were examined by the ship's medical staff. They sustained minor injuries, Benson said.
"They appear to be in satisfactory condition and we hope that no further medical attention will be needed," Benson said.
They will have the option of continuing on the trip or returning home when the ship reaches port. The ship was on its way to Costa Maya on Mexico's coastline, Benson said.
Grand Princess was carrying 2,783 passengers on a seven-day tour of the western Caribbean.