Besides the emir, senior members of the ruling Al-Sabah family hold all top cabinet posts.
But unusually for the oil-rich Gulf Arab states, Kuwait has an elected parliament with powers to hold ministers to account.
That has led to repeated standoffs between lawmakers and the ruling family and this is the seventh general election in a decade.
It comes against a backdrop of discontent among Kuwaiti citizens over mounting cutbacks in the cradle-to-grave welfare system they have long enjoyed as a slump in world oil prices hits government revenues.
The emir dissolved the last parliament after MPs called for ministers to be grilled over the cuts to state subsidies.
Women, who have had the right to vote in Kuwait since 2005, were already queuing outside polling stations when voting began at 8 am (0500 GMT).
"We want the next parliament to stop the government from hiking prices," said pensioner Maasouma Abdullah.
"We want the government to begin taxing the rich and pay great attention to the low-income sections," said Maha Khorshid, an education ministry employee.
"We want the next assembly and government to approve more development projects."
Opposition candidates campaigned heavily for economic and social reform and an end to what they charge is rampant corruption.
Nearly all opposition parties shunned the previous parliamentary elections in July 2013 and December 2012.
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It came after a court decision overturned a February 2012 vote which the opposition won and the government changed the electoral rules.
Most of the opposition has now ended the boycott over alleged gerrymandering by the ruling family-led government.
- Bleak economic backdrop -
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.
And the emirate has fewer alternatives than its Gulf neighbours, partly because it does hold elections, analysts say.
"It has built an economic model completely funded by oil and natural gas revenue to support its workforce, but with its empowered parliament it has less flexibility than any other state in the region to abandon that model," US-based intelligence firm Stratfor said in a recent report.
"Other members of the Gulf Cooperation Council are modeling their economic reforms after Dubai's financial, investment and real estate-led model, but Kuwait cannot easily follow suit."
Polls are due to close at 8 pm (1700 GMT) with first results expected after midnight (2100 GMT).
The opposition is fielding 30 candidates among a total of 293 hopefuls who include 14 women.
Kuwaiti citizens make up around 30 percent of the emirate's population of 4.4 million. A total of 483,000 are elegible to vote.
The proportion of expatriates in the population is smaller than most other Gulf states -- with knock-on effects for Kuwait's prospects for reform.
"Unlike the United Arab Emirates, it cannot accept a foreign workforce that takes the key private sector jobs like Dubai has. In Kuwait, most foreign workers perform the jobs that Kuwaitis do not want to perform," said Stratfor.