A Russian Il-96 plane carrying the diplomats and their families landed at Moscow's Vnukovo airport at 2:05 am local time, after having taken off from Washington on Sunday, state television said.
State television showed the diplomats and their families gathering their luggage on the tarmac in the rain before heading inside the terminal.
Plane with expelled diplomats leaves US: Russian media
US intelligence says the Kremlin ordered a hack-and-release of Democratic Party and Hillary Clinton campaign staff emails in a bid to put Donald Trump in the White House.
Moscow has repeatedly dismissed the allegations.
The expulsions of the diplomats - described as intelligence operatives based at the Russian embassy in Washington and the consulate in San Francisco - were part of a package of sanctions ordered by President Barack Obama Thursday in the final weeks of his administration.
Grizzly Steppe: how the US says Russia hacked the election
Obama also ordered the closure of two Russian compounds in New York and Maryland that the United States says were used "for intelligence-related purposes."
Russian President Vladimir Putin last week rebuked the outgoing president for "unfriendly steps" amounting to "a provocation aimed at further undermining Russian-American relations."
The Kremlin strongman warned that Russia reserved the right to respond but refrained from ordering the tit-for-tat expulsion of American diplomats from Russia, saying that Moscow's next move will be "based on the policies pursued by the administration of president Donald Trump."
Russia to US: prove hacking allegations or shut up
Putin's decision has been interpreted as a sign he is looking to Trump to rebuild US-Russian ties after the US presidential inauguration later this month.
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