Benson Radiology will take over medical imaging services at Murray Bridge's hospital in February, the state government has revealed.
Patients will no longer need to pay a gap fee when getting X-rays or ultrasounds after the changeover.
All SA Health staff currently working in the unit will be kept on.
Health and Wellbeing Minister Stephen Wade said the state government was committed to improving regional South Australians' access to world-class health care and keeping out-of-pocket costs down.
"This new contract ... is a major win for our patients," he said.
State MP Adrian Pederick described the announcement as a great outcome after a period of uncertainty.
SA Health's contract with Benson will last for five years, with an option to extend for another two or three.
The department had been preparing to outsource operation of the hospital's X-ray unit since February.
The change was opposed by the Public Sector Association, mainly on the grounds that it could lead to higher fees for patients; and the state opposition.