The celebrity chef closed seven of his restaurants last year, as well as his Union Jacks chain.
The Sun reports that Oliver could be informing staff of the possible closures as early as next week.
A source described the news as 'devastating,' and added that the timing is 'terrible.'
'Officially, staff will be told the closures are because of company streamlining,' the source said.
'But hard-working, loyal employees who have given their all for Jamie Oliver now fear being tossed aside like garbage.'
A spokesperson for Oliver's chains said, 'The Jamie Oliver Restaurant Group can confirm it is exploring plans to restructure its Jamie's Italian restaurant estate in the UK, to ensure the business is in good shape for the future.
'As part of this review, we are in conversation with our stakeholders, but no final decisions or proposals have been made at this stage.'