According to WalesOnline, the signs for the seafront restaurant with rooms have been removed; and the building's landlord, Richard Hayward, has claimed it will not reopen there after lockdown.
Hayward told the publication that the business was no longer financially viable, and that during the period of closure he made the decision that the restaurant could not return to his premises.
"It was a successful restaurant, but the pandemic has not been good for Michelin-starred restaurants," he said.
"It has changed the way people are thinking about going out to eat.
"The debt was rising and we had to tell them to go."
Sommerin opened the Penarth restaurant, which he ran with his wife Louise, in 2014.
It was the chef's first solo venture, having previously spent more than a decade cooking at the Michelin-starred Crown at Whitebrook in South East Wales (now simply known as The Whitebrook) - first as a sous chef, and later as head chef.
Restaurant James Sommerin was awarded its first Michelin star in the 2017 Guide.
Last November it was also reported by WalesOnline that Sommerin was to open a new restaurant in the Goodsheds development in the town of Barry.
Having closed Restaurant James Sommerin in March this year as a result of the Government-mandated shutdown of the hospitality sector, the chef worked alongside his wife and daughters to prepare thousands of meals a week to feed hospital workers on the front line of the Coronavirus crisis.
BigHospitality has contacted Sommerin's representatives for comment regarding the restaurant's closure.