Gross domestic product (GDP) shrank an annualised 0.8% on-quarter in the three months to June, according to advance trade ministry estimates that were below market expectations.
The decline was due to a 19.4% quarter-on-quarter contraction in the manufacturing sector, the Trade Ministry said, citing a fall in the output for electronic goods, a main export for the Southeast Asian city-state.
On a year-on-year comparison, GDP rose 2.1%, but much slower than the 4.7% growth during the first quarter.
Growth in the construction sector moderated to 5% from 6.4% the year before, while services expanded at a slower pace at 2.8% from 3.9%.
Sectors such as construction are under pressure owing to tighter government rules for foreign labour aimed at placating public anger over a surge in immigration, analysts said.
Monday's GDP figures are based on two months of data and are used to gauge the economy's performance ahead of the release of the final numbers.
The weakness in manufacturing industries, which contribute a fifth of Singapore's economy, pose "downside risks to our 2014 GDP growth outlook," United Overseas Bank said in a commentary.
Capital Economic research house said however that "we still expect the ongoing recovery in advanced economies to underpin reasonably healthy growth over the rest of the year".
The government expects GDP to grow 1-3% this year, barring downside risks.