Follow the latest news on the US midterm elections 2022
"Shared power curbs the worst excesses of both parties, therefore I recommend voting for a Republican Congress, given that the Presidency is Democratic," Mr Musk said in a tweet on Monday to his more than 110 million followers.
Republicans are favourites to win a majority in the House of Representatives, with the Senate thought to be a toss-up by nonpartisan election forecasters, Reuters reported.
Democrats currently control both houses.
Mr Musk, the world's richest person and chief executive of Tesla, took over Twitter in a $44 billion deal last month and has engaged in drastic measures, including firing half of its staff and planning to charge for blue check verification marks.
His absolutist stance on free speech has led some groups to warn against a rise in misinformation and some advertisers to pull their spending. A crackdown on users impersonating Mr Musk prompted Twitter to suspend US comedienne Kathy Griffin.
Later, he added that he was "open to the idea of voting Democrat again in the future" and said he had historically been an independent who had voted for Democrats.
Mr Musk has been critical of the Biden administration and Democrats for their proposals to tax billionaires and give more tax incentives to union-made electric vehicles. Tesla does not have unions at its US factories.
Republicans could use a majority in either chamber to bring Mr Biden's agenda to a halt and launch potentially politically damaging investigations into his administration and family.
Kyle Kondik, from the University of Virginia's Centre for Politics, said it was unlikely Mr Musk's words would influence the election's outcome.
Asked about Mr Musk's comments, White House press secretary Karine Jean-Pierre said: "The president has often spoken about the importance of voting, and I'm just going to leave it there as to not get involved in any kind of election conversation."
Former Republican Speaker of the House Newt Gingrich described Musk's comments as "very encouraging".