Kremlin spokesman Dmitry Peskov told the Interfax news agency on Tuesday, "Yes, I've gotten sick. I'm being treated."
Peskov, 52, has been Putin's spokesman since 2008, but started working him with in the early 2000s.
Russians who have the virus but light or no symptoms of illness are allowed to stay home, and it wasn't immediately clear if Peskov's hospitalization reflects the gravity of his condition or was an extra precaution.
Reporters from the Kremlin pool said on Twitter that Peskov was last seen in public on April 30 "at a meeting with Vladimir Putin." It was not clear whether it means the two were in the same room, as Putin has been conducting all his meetings via teleconference in recent weeks.
Since early in the outbreak, the Russian president minimized meetings and switched to holding daily video calls with Cabinet members and aides.
Peskov's announcement comes just a day after Putin said Russia was successful in slowing down infections and announced easing some of the nationwide lockdown restrictions.
Russia has reported more than 232,000 confirmed coronavirus cases as of Tuesday. Hours before Putin made televised remarks Monday about ending the country's partial economic lockdown, health officials reported a daily record of over 11,600 new cases.
Russian Prime Minister Mikhail Mishustin revealed on April 30 that he had tested positive for the virus and planned to self-isolate. Putin asked the prime minister to call him after checking into a hospital. (AP) SCY