In parts of Asia, the threat of terrorism loomed large, and a bombing at a market in Indonesia killed eight people and wounded 45.
But celebrations worldwide were generally jubilant, in contrast with last year when the devastation of the Indian Ocean tsunami led many countries and individuals to cancel festivities.
Hundreds of American soldiers in Iraq got a special show from "American Idol" singer Diana DeGarmo and other entertainers at Camp Victory in Baghdad.
More than 2 million Brazilians were expected at jam Rio de Janeiro's famed Copacabana Beach for the largest fireworks extravaganza in the city's history. Officials planned to set off nearly 25 tons of fireworks.
London saw many subway workers walk out just hours before a huge open-air celebration in Trafalgar Square and other parties around the capital.
"I am not worried about the strike; I'm just going to take a cab or use the buses," said Matthew Lapalus, a 22-year-old Frenchman who came to London to celebrate New Year's Evens of fireworks..
London Underground said it hoped workers not affiliated with the striking RMT union would keep much of the network running. By early evening, only about 30 of the Tube's 275 stations were closed as managers sought to keep some trains going.
In France, 25,000 police were on alert, fearing a repeat of arson attacks and rioting that swept the country for three weeks starting in late October.
"The orders I have given are very strict," said French Interior Minister Nicolas Sarkozy. "When there are delinquent acts there will be arrests. Those guilty must be accountable for their acts."
Burning cars is common in troubled French neighborhoods — dozens of vehicles are set afire on an average night and in recent years the figure has risen to about 300 on New Year's Eve. But police were especially cautious this year and a state of emergency imposed during the rioting was still in effect.