The Republican Party has seized control of the US House with a slim majority far smaller than the party had been banking on.
NBC and CNN projected the victory for Republicans with at least 218 seats in the 435-member House of Representatives.
Republicans, however, failed to take control of the Senate in a historically weak performance in the midterm elections.
Republicans had hoped to see a "red wave", giving them control of both houses and hence an effective block over most of Biden's legislative plans.
But instead, Democratic voters turned out in force. And Republicans lost ground with candidates rejected by moderate voters as too extreme.
The news came one day after former president Donald Trump announced a new run for the White House.
Biden's party flipped a key Senate seat in Pennsylvania and held onto two more in battleground states Arizona and Nevada, giving them an unassailable majority in the upper chamber with 50 seats plus Vice President Kamala Harris' tie-breaking vote.
The Senate oversees the confirmation of federal judges and cabinet members, and having the 100-seat body in his corner will be a major boon for Biden.
With narrowly securing a legislative base, Republicans are now set to to oppose President Joe Biden's agenda for the final two years of his term.