They were visiting the eastern state of Odisha and the millionaire, who was also a local politician, had just celebrated his birthday at the hotel.
Antov was a well known figure in the city of Vladimir, east of Moscow.
Last summer he denied criticising Russia's war in Ukraine after a message appeared on his WhatsApp account.
The millionaire's death is the latest in a series of unexplained deaths involving Russian tycoons since the start of the Russian invasion, many of whom have openly criticised the war.
Reports in Russian media said Mr Antov, 65, had fallen from a window at the hotel in the city of Rayagada on Sunday. Another member of his four-strong Russian group, Vladimir Budanov, died at the hotel on Friday.
Superintendent Vivekananda Sharma of Odisha police said Mr Budanov was found to have suffered a stroke while his friend "was depressed after his death and he too died". The Russian consul in Kolkata, Alexei Idamkin, told the Tass news agency that police did not see a "criminal element in these tragic events".
Tourist guide Jitendra Singh told reporters that Mr Budanov may have "consumed a lot of alcohol as he had liquor bottles".
Pavel Antov founded the Vladimir Standard meat processing plant and in 2019 Forbes estimated his fortune at some $140m (£118m) at the top of Russia's rich list of lawmakers and civil servants.
He played an important role at the legislative assembly in Vladimir, heading a committee on agrarian policy and ecology. The assembly's deputy chairman Vyacheslav Kartukhin said he had died in "tragic circumstances".
Late last June he appeared to react to a Russian missile attack on a residential block in the Shevchenkivskyi district of Kyiv that left a man dead and his seven-year-old daughter and her mother wounded.
A WhatsApp message on Antov's account described how the family were pulled out of the rubble: "It's extremely difficult to call all this anything but terror."
The message was deleted and Antov then posted on social media that he was a supporter of the president, a "patriot of my country" and backed the war.
The WhatsApp message had come from someone whose opinion on the "special military operation in Ukraine" he strongly disagreed with, he insisted. It had been posted accidentally on his messenger and was a highly annoying misunderstanding, he said.
Several high-profile Russian tycoons have died in mysterious circumstances since the war began.
In September the head of Russia's oil giant Lukoil, Ravil Maganov, apparently fell from a hospital window in Moscow.