The September polls – the most inclusive in a decade – had seen opposition members clinch 28 out of 50 seats, giving them a parliamentary majority.
Kuwait's Constitutional Court has annulled the results of last September's parliamentary election, in which the opposition made gains, and ruled in favour of reinstating the previous government, state media said.
Sunday's move comes at a time of renewed friction between the elected parliament and government and follows the reappointment this month of the country's prime minister, whose government had resigned in the stand-off with parliament.
Kuwait's crown prince last year dissolved parliament and called early polls in an effort to end prolonged domestic political feuding that has hindered fiscal reform.
However, Justice Mohammad bin Naji on Sunday said the court had declared the dissolution of parliament as void and had annulled the early elections held in September.
"The constitutional authority of the dissolved parliament shall be restored as of the date of this ruling," he told the court session attended by reporters.
READ MORE: Kuwait's government resigns amid struggle with assembly
Kuwait, an OPEC oil producer, bans political parties but has given its legislature more influence than similar bodies in other Gulf monarchies.
Frequent political bickering has often led to cabinet reshuffles and dissolutions of parliament, hampering investment and reforms aimed at reducing the country's heavy reliance on oil revenue.
"Kuwait does not deserve such farces," MP Saleh Ashour said on Twitter after the court ruling.
A lawmaker from the dissolved assembly, Abdullah Al Turaiji, welcomed the move as "correcting the government's mistake in dealing with parliament".
Political stability in Kuwait has traditionally depended on cooperation between government and parliament.
While Kuwait's leadership has responded to some opposition demands, including the pardoning of political dissidents, key reform proposals such as a public debt law continue to face legislative gridlock.
READ MORE: Kuwait crown prince reappoints Sheikh Ahmad Nawaf al Sabah as PM