The constitutional court in Thailand has rejected an opposition request to annul the election on 2 February, citing insufficient grounds.
The Democrat Party argued that the poll violated the constitution for several reasons, including that it was not completed in one day.
The government blamed the delay on the opposition blocking polling stations.
Thailand has been in a political crisis since anti-government protests began in November.
They were sparked by an amnesty bill which critics said would allow former leader Thaksin Shinawatra to return to Thailand.
The demonstrators have since called for the government of Prime Minister Yingluck Shinawatra, Thaksin's sister, to make way for an interim replacement that would bring in anti-corruption reforms.
The BBC reports Ms Shinawatra called the election in the hope of defusing the crisis. But the Democrats refused to contest the election.
A correspondent said the opposition has not exhausted legal avenues for blocking the government. They hope a corruption investigation into Ms Yingluck and other ministers will prevent her from forming a new government.