Cruise line age requirements

Families with Children
Most cruise lines welcome children to travel on their ships, though infants and pregnant women are subject to some restrictions(see next post)
Families booking more than one cabin may be subject to minimum age requirements for kids staying in a separate cabin. I can check these requirements for you, once you have found a cruise you are interested in.
Guests Under 25 Years of Age:
All cruise lines require that at least one person in each cabin meets a minimum age requirement. The information that follows was provided by the cruise lines at the time of this writing, is subject to change.
The lowest minimum age requirement for any cruise line is 18. The following cruise lines require that at least one person in each cabin is 18 or older: American West Steamboat Company (Majestic America), Cruise West, Cunard, Delta Queen (Majestic America), Fred. Olsen Cruise Line, Oceania, Orient Lines, P&O Cruises, Peter Deilmann, Regent (Radisson) Seven Seas Cruises, SeaDream, Star Clippers, and Uniworld.
The following cruise lines require that either 1) All passengers in a cabin must be 18 or older, or 2) If anyone in the cabin is younger than 18 years old, someone in the cabin must be 21 or older: Clipper, Disney Cruise Line, GAP Adventures, Silversea and Viking River Cruises.
The following cruise lines require that at least one person in each cabin is 21 or older: Azamara, Celebrity, Costa (25 for March and April sailings), Crystal Cruises, Voyages of Discovery, MSC Cruises, Norwegian Cruise Line, Princess Cruises, Royal Caribbean and Seabourn Cruise Line.
The following cruise lines require that either 1) All passengers in a cabin must be 21 or older, or 2) If anyone in the cabin is younger than 21 years old, someone in the cabin must be 25 or older: Carnival, Holland America and Windstar Cruises.
One exception to these age requirements is made for underage married couples, who as long as they are both 18 are allowed to board unaccompanied. These couples may be asked to show proof of their marriage.
Your age on the date of sailing is generally considered your age for the length of the cruise.
Consumption of Alcohol:
Once you've left port, the minimum age for the consumption of alcohol varies by cruise line.
Fred. Olsen Cruise Line, GAP Adventures, Oceania and Regent Seven Seas allow all passengers 18 and older to consume any type of alcoholic beverage they choose.
The minimum drinking age for all alcoholic beverages on all Azamara, Celebrity and Royal Caribbean ships is 21. However, on cruises departing from European and South American countries, where the legal drinking age is typically lower than 21, a parent who is sailing with his or her son(s) and/or daughter(s) who is between the ages of 18 to 20, may sign a waiver allowing the 18 to 20 year old to consume alcoholic beverages.
American West Steamboat Company (Majestic America), Carnival, Clipper, Costa, Cruise West, Crystal, Cunard, Delta Queen (Majestic America), Voyages of Discovery, Disney, Great American River Journeys, Holland America, MSC Cruises, Norwegian, Orient, Peter Deilmann, Princess, Seabourn, SeaDream, Silversea, Star Clippers, Uniworld, Viking River Cruises and Windstar require passengers to be at least 21 to consume any type of alcohol.
Gambling Onboard:
Gambling, a popular form of entertainment on cruise ships, also has age restrictions which differ between cruise lines. Carnival, Fred. Olsen Cruise Line, Holland America, Norwegian, Oceania, Orient, Regent Seven Seas and SeaDream require passengers to be 18 or older to play in the shipboard casinos. Celebrity and Royal Caribbean require passengers to be 18 or older to play in casinos, except for Alaska cruises (passengers must be 21 or older). Crystal, Cunard, Voyages of Discovery, MSC Cruises, Princess, Seabourn, Silversea and Windstar restrict the casinos to travelers 21 and older. Costa requires those gambling in the casinos to be 25 or older.