The People's Action Party (PAP) won an absolute majority of 83 seats in the 89-member Parliament. The opposition Workers' Party won six seats.
"I am deeply humbled by the confidence Singaporeans showed in me and my team and the heavy responsibility voters have entrusted to us," Lee was quoted as saying by Channel News Asia.
The PAP, which has been ruling the city-state for the past 50 years, got 69.86 per cent of the popular vote, an increase of almost 10 percentage points from its share in 2011.
This was also the first general election without founder prime minister Lee Kuan Yew who died in March. He was the father of Prime Minister Lee Hsien Loong.
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"I am happy with the outcome of the election. We won 83 seats and what was particularly satisfying was that we won back Punggol East," Lee said at an early-morning press conference after the final results were announced. Punggol was previously held by Workers' Party.
"It's a good result for the PAP, but it is an excellent result for Singapore," the channel quoted Lee as saying.
The PAP was challenged at the hustings on issues including new migrants, foreign workers competing for jobs with Singaporeans, high costs of living and housing, stressed transportation system and the central provident fund, the old age based withdrawal of which was questioned.
Lee said the high figures the party received would not have been possible without support across all race and age groups, in particular from the young who showed that they understood what was at stake and how the Government was trying to secure their future.