The People's Action Party (PAP) on Saturday won 66.6% of the votes cast, down from 75.3% in the 2001 poll.
But it held on to 82 seats in the 84-seat parliament, giving it an almost unchallenged free hand to continue its pro-business policies.
"I am very happy that the PAP has been returned to government," Lee Hsien Loong, 54, fighting his first election as prime minister, said.
"Now that we have a new leadership team in place, it will see Singapore through the next 15-20 years."
The city-state of 4.4 million people, which borders Malaysia, is an important regional manufacturing, trading, and financial services centre which relies heavily on foreign investment and its image as a secure business environment.
Status quo result
The PAP had hoped for a crushing victory by winning every single seat in parliament.
Lee, the eldest son of former prime minister Lee Kuan Yew who led Singapore to independence from Malaysia in 1965, was appointed in August 2004 without an election.
"It's very much a status quo result. The PAP was denied the clean sweep that it sought, but held on to its own seats and there were no further gains by the opposition," said Cherian George, a political analyst at Nanyang Technological University.
Opposition parties improved the
margin of victory in two seats
Although the opposition failed to build on its two parliamentary seats, Low Thia Khiang of the Workers' Party and Chiam See Tong of the Singapore Democratic Alliance saw their winning margins improve.
"It shows that the people of Singapore want more opposition in parliament," Chiam said on state television.
The opposition parties had fielded candidates for more than half the seats in parliament for the first time in 18 years.
In Lee's own constituency, a group of Workers' Party candidates which the incoming prime minister had dubbed "the suicide team" managed to win one in three votes.
"It's not about policies, it's about having an opposition, rather than a single-party country," Song Seng Wun, an economist at CIMB-GK Research, told Reuters.
Song added that the PAP had received a comfortable enough endorsement to carry on with its economic restructuring.
Singapore is building a biotech
industry and two casinos
With its electronics manufacturing sector under threat from low-cost China, Singapore is trying to strengthen its services sector. It has built up a biotech industry and plans to build two casinos at a total cost of S$5 billion to boost tourism.
Lee, who is also the finance minister, can attribute his success to the strong economy, an array of financial incentives for voters, and efforts to silence opposition criticism.
In the run-up to the election, the government gave cash handouts to low-income and elderly Singaporeans and army conscripts, and promised hundreds of millions of dollars to renovate public housing in wards which supported the PAP.
On Friday, Lee told an election rally that the S$118 billion (US$75 billion) economy had expanded by more than 10% in the first quarter from a year ago and said full-year growth could beat the government's earlier forecast of 4-6%.
The jobless rate, at 2.6%, is the lowest since the second quarter of 2001.
Opposition candidates faced
personal attacks and lawsuits
Like the previous three elections, this one was overshadowed by defamation lawsuits and personal attacks - a time-worn PAP tactic that has bankrupted some opposition leaders, thus disqualifying them for parliament.
Just a week before the polls, Lee and his father launched a defamation suit against the Singapore Democratic Party and its leaders.
During the campaigning period, the PAP repeatedly condemned an opposition candidate from the Workers' Party as a "liar", urging the party to drop him after he wrongly claimed that the elections office had lost one of his election forms.