The group, which includes the Jamie's Italian chain, Barbecoa and Fifteen, has appointed KPMG as administrators.
"I would like to personally thank all of the United Kingdom restaurant staff, many of whom have put their hearts and souls into this business for a decade", Mr Oliver wrote.
The process does not affect Mr Oliver's other companies, which handle his media and licensing deals, while the worldwide branch of Jamie's Italian is also unaffected.
More than 25 overseas Jamie's Italians, and Fifteen in Cornwall, all of which are run by franchisees, are unaffected by the administration. "And we did exactly that".
He has also campaigned for healthier eating, including in school meals.
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In March, Boparan Restaurant Group (BRG) said it planned to close more than a third of its Giraffe and Ed's Easy Diner outlets, while Carluccio's, Prezzo, Strada and Gourmet Burger Kitchen closed branches in 2018.
His chain is the latest victim of a tough trading environment on the UK High Street.
The administration, first reported by Sky News, comes two years after Mr Oliver's business went through a painful restructuring to offload unprofitable sites.
In 2017, he closed the last of his Union Jacks restaurants and also shut his magazine Jamie, which had been running for nearly 10 years.
Oliver's media business, which includes his cookery books and TV shows, continues to thrive, according to accounts published past year, but his licensing business, of which he owns more than half in partnership with other investors and includes cooking equipment and homewares, has also seen profits fall.