The site was owned and operated by the Cornwall Food Foundation, despite its use of the Jamie Oliver group name. The outpost was one of the last remaining Jamie Oliver sites in the UK.
Some 100 jobs will be lost in the closure, with 70 positions within the restaurant and 30 positions within the Foundation ending with immediate effect.
In a statement, the board of directors for Fifteen Cornwall said: “ [We] are deeply saddened to announce that, following an independent financial review, both the restaurant and charity will cease trading today with immediate effect.
“The boards have taken the necessary steps towards liquidating both companies and our nominated liquidators will communicate with creditors and all affected parties as soon as possible.”
It continued: “As a charity and social enterprise restaurant we have welfare and safeguarding responsibilities which we are doing our utmost to resolve.
“We are talking with partners to find a way for the support for people we work with to continue, including those on the Fifteen training programme and Food for Change.”
Matthew Thomson, chief executive of the Cornwall Food Foundation, said: “This is an incredibly sad day for everyone and we will try our best to support those who have been impacted.
“I am profoundly sorry for the hurt, loss and distress this announcement will undoubtedly cause.”
He added: “We are extremely grateful to all our loyal customers and amazing suppliers and to the partners, staff and trainees that have made Fifteen Cornwall and the Cornwall Food Foundation so special for almost 14 years.”
As Fifteen Cornwall was run under license with no financial attachment to the group, it continued to operate despite these closures.