Children under the age of 12 are being stopped from visiting a hospital without permission in a bid to reduce the spread of infections.
An adult must also accompany youngsters on visits to Russells Hall Hospital in Dudley under the new rules.
Other changes are a strict four-hour visiting period in the evening and only two visitors per patient at a time.
A spokeswoman said the hospital was concerned with the needs of patients and wanted to maintain high standards.
She said: "We have the lowest MRSA rates in Birmingham and the Black Country and we would like to keep it that way."
She said wards had a mixture of patients on them and parents should be responsible for asking if it was appropriate to bring children onto them.
"In some acute surgical wards there are emergency situations and it is not very good for children to be around that environment anyway," she said.
"In others there are various different infections and it is not healthy for children."
An open visiting policy was previously in place at the hospital meaning it was up to individual ward managers to decide on rules. The spokes-woman said patients groups were consulted on the changes and had welcomed them.