The party said in a statement that the detentions happened as the rally was ending, and that its Moscow branch was working to get those who were detained - mostly young people - released.
The rally marked the anniversary of the Kremlin's 1993 crushing of a parliamentary uprising.
The Telegram news channel Ostorozhno Novosti said protesters chanted slogans including "Freedom for political prisoners," "For fair elections" and "Down with the tsar".
The rally came as public frustration has been simmering in Russia during the intensifying Ukrainian drone attacks deep inside the country.
The strikes have hit oil refineries and warehouses, caused fuel shortages and disrupted daily life including in Moscow.
The October 1993 violence capped a long stand-off between president Boris Yeltsin and hardline MPs who opposed his painful free-market reforms.
After Yeltsin ordered parliament disbanded and demonstrators supporting the MPs tried to seize the state TV broadcasting centre, he sent in the military which used tanks to shell the parliament building.
Authorities said 123 people were killed while unofficial estimates put the toll in the hundreds.
The Communist party has been a leading force in parliament since the 1990s, led for more than three decades by 82-year-old Gennady Zyuganov, a former Soviet official.
Throughout Putin's rule of over a quarter-century, the Communists have criticised some aspects of government policy but carefully avoided any criticism of him.
They steadfastly support the war in Ukraine.
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