The man reportedly apologized to the 15-year-old victim and her family for the assault last month.
The Pakistani has admitted to attacking the girl after a second test of his DNA matched a sample taken from the victim.
The 21-year-old allegedly told police that he had seen the girl sitting on rocks on the Chrysi Akti beach in Paros and had tried to steal her cellphone. When she resisted he beat her head against the rocks until she passed out.
The girl is still in critical condition in an Athens hospital after suffering serious head injuries in the assault. Initial reports had indicated that the 15-year-old had been sexually assaulted but police did not confirm this.