The 5.5 billion US dollar Marina Bay Sands, built by US gaming giant Las Vegas Sands, opened at the locally auspicious time of 3:18 pm (0718 GMT). The number eight sounds like the word for prosperity in Chinese.
It is Las Vegas Sands' latest big-time bet on the future of Asia's gaming industry and is its first casino in Asia outside Macau.
Las Vegas Sands chairman Sheldon Adelson said he expects to recoup his Singapore investment in five years.
"Most of the high-end players are reputable business people. They have to travel anyway so they typically would travel to the major cities, like Hong Kong and Singapore, wherein they do business," he told reporters.
Singapore gave the green light for casino gambling in 2005, setting off a flurry of construction that went ahead despite the city-state slipping into recession in 2008 because of the global financial crisis.
Its first casino, the 4.4 billion US-dollar Resorts World Sentosa built by Malaysia's Genting Group, opened for business on February 14.
Marina Bay Sands was originally set to open at the end of 2009 but faced repeated delays caused by a number of factors, including material and labour shortages and financial problems due to the downturn.
Tuesday's opening includes the casino and 963 out of 2,560 hotel rooms, a portion of the shopping mall, some restaurants, an exhibition centre and the events plaza.
The remaining hotel rooms and suites, a skypark and more shops will open on June 23, while a museum, theatres and other stores will start operations later in the year, the management said.
Officials hope the casinos will help Singapore achieve a target of attracting 17 million visitors a year generating over 21 billion US dollars by 2015, supporting the services sector and reducing the role of manufacturing in the economy.
"This second casino is another boost to the economy, which has been doing much better," said economist David Cohen at research house Action Economics.
"It should support tourist arrivals, and the retail sector should benefit from that especially now in the midst of the improving global outlook," he told AFP.
Singapore's economy surged 13.1 percent in the first quarter from a year ago, prompting the government to sharply upgrade its growth projection this year to 7-9 percent from 4.5-6.5 percent.
Cohen however is projecting higher growth of 9.5 percent this year.
"Singapore already enjoys a very convenient (global air) transportation network which makes this an attractive place for people to come from around the world," he said.
Marina Bay Sands is designed to cater to the corporate and convention crowd while Resorts World is aimed at families.
The Marina Bay Sands casino will offer 600 gaming tables, more than 1,500 slot machines and over 30 private gaming rooms. It occupies four floors, the bottom two for mass gaming and the upper section for premium players.
The Resorts World complex, located on Sentosa island, includes Southeast Asia's only Universal Studios movie theme park, hotels, restaurants and convention facilities.