Kuwait opposition groups and their allies had bagged nearly half parliament's 50 seats Sunday, raising fears of fresh political wrangling in the oil-rich Gulf state.
The opposition and its allies won 24 seats, according to official results announced by the election authority.
The Islamist, nationalist and liberal opposition contested Saturday's election after a four-year boycott protesting the government's amendment of the key voting system.
Around half of the successful opposition MPs are Islamists from a Muslim Brotherhood-linked group and Salafists.
Only one woman was elected and the Muslim Shiite minority was reduced to six seats from nine in the previous house. A third of the new parliament are new young members.
The polls saw a turnout of around 70 percent amid divisions over cuts in subsidies due to falling oil revenues.
Emir Sheikh Sabah al-Ahmad Al-Sabah called the snap polls after dissolving the previous parliament due to a dispute over raising petrol prices.
Kuwaiti voters dealt a heavy blow to members of the outgoing parliament, retaining only 40 percent of them as two of three cabinet ministers failed in their bid for re-election.
A majority of those elected have openly said they will oppose any austerity measures by the government to boost non-oil income.
The government's overwhelming control in the previous assembly has been reduced to a fragile majority.
The majority is because unelected cabinet ministers also become members of parliament, helping to consolidate the grip of the Al-Sabah ruling family on the house.
Unlike other oil-rich Gulf Arab states, Kuwait has an elected parliament with powers to hold ministers to account, even though senior members of the ruling family hold all top cabinet posts.
The set-up has led to repeated standoffs between lawmakers and the ruling family and Saturday's vote was the seventh general election in a decade.
But the strength of the opposition allows them to grill ministers and possibly even vote them out of office.
The election comes with Kuwait facing its most acute budget crisis in years. Oil income, which accounts for 95 percent of government revenues, has nosedived by 60 percent over the past two years.
The OPEC member posted its first budget deficit of $15 billion last year following 16 years of surpluses.
Kuwaiti citizens make up around 30 percent of the emirate's population of 4.4 million.