Representatives from the GMB union, which represents some of the staff at the hospital, stood outside the main entrance on Armthorpe Road carrying banners and playing music.
They were joined by members of Doncaster trades council, who expressed their support for the protest over fears that some services at the trust may be transferred to a wholly owned subsidiary.
The protest was time to coincide with a governors meeting, which the union believed was due to discuss the issue.
She said: "No one came out to speak to us, but we made it clear that that we are not happy about the idea."
The union says it fears that the trust wants to create a new company and run NHS services from it, and opt out of national agreements on pay terms and conditions. They say workers could be affected by this.
They added: “We always explore all options to aid us in the delivery of high quality patient care and making best use of public money.
“We have not made any decisions or expressed any preferences in regards to taking a Wholly Owned Subsidiary forward at this time. If this were to change, we would communicate any proposals well in advance.”