The phlebotomists have been on strike for 350 days in the dispute over pay and job evaluations.
Following talks with Gloucestershire Hospitals NHS Foundation Trust, staff have now accepted a deal that will see their pay and roles reviewed by an independent job evaluation panel.
They had argued their work had been undervalued for years, despite the skills and responsibilities required to take and handle blood samples.
As part of the agreement, the trust has committed to recognise the specialist nature of the phlebotomy role and to consult staff on the future of the service, says the union.
The decision means the dispute will end and staff will return to work on Monday (16 March).
Unison South West regional secretary, Tim Roberts, said: ‘Phlebotomy staff have shown incredible determination throughout this lengthy dispute.
‘After nearly a year of strike action, they're looking forward to going back to their jobs and putting their expertise to good use.'
