A 21-year-old inmate has been charged with assaulting Peter Tobin at Saughton Prison in Edinburgh.
Mr Tobin, 61, had been due to appear at Linlithgow Sheriff Court on Thursday morning charged with the murder of teenager Vicky Hamilton.
But the hearing was postponed to allow him to receive treatment for cuts and bruises at Edinburgh Royal Infirmary.
Mr Tobin was attacked on Wednesday in the prison's protection wing, where vulnerable prisoners are housed.
A spokesman for Lothian and Borders Police confirmed a 21-year-old man had been charged in relation to the assault, and would be reported to the procurator fiscal.
The accused man is understood to be a serving prisoner at Saughton.
Mr Tobin had been expected to return to court for a full committal hearing on Thursday, a week after he was remanded in custody having been accused of 15-year-old Vicky's murder.
The eight-day deadline for Mr Tobin to attend the hearing will expire on Friday. If he is unable to appear by then, the Crown will seek an extension from the court so he can attend at a later date.
A spokeswoman for the Crown Office had earlier confirmed: "Peter Tobin will not be appearing at court today and we will not be in a position to say whether he'll appear on Friday until tomorrow morning."
The spokeswoman would not confirm that Mr Tobin's non-appearance was directly linked to the attack.
A Scottish Prison Service spokesman said: "A prisoner was subject to an assault and has been taken for medical treatment."
Mr Tobin once lived at the three-bedroom council house in Irvine Drive, Margate, where the bodies of Vicky and Dinah McNicol, 18, from Essex, were found last week.
Mr Tobin was due at court for a second appearance
Vicky was last seen at a bus stop in Bathgate's George Square, just after 1735 GMT on 10 February, 1991.
Eyewitnesses said that she was sitting on a bench eating chips.
Vicky had been returning from Livingston, where she had been staying with her sister, to her home in Redding, near Falkirk.
Friends and relatives had joined Vicky's father Michael outside the court as they waited for the prison van to arrive.
They also gathered outside the court for Mr Tobin's first appearance last week and there were angry scenes as the accused entered and left on that occasion.
Speaking to reporters on Thursday, Mr Hamilton said he was making arrangements for Vicky's funeral, which would take place after Christmas.
He said: "I don't want to have to spend all my Christmases thinking that I buried my daughter at Christmas or just before, so we've asked the CID if we can hold it back until after Christmas and New Year."