Jonty Bravery, 18, entered his plea during a short hearing at the Old Bailey in London on Friday.
He was remanded in custody by the judge, Recorder of London Nicholas Hilliard QC, ahead of his sentencing hearing at a later date.
The victim, who cannot be named because of his age, continues to recover slowly in his native France after spending months in intensive care.
Writing on a GoFundMe page last month, which has raised around £130,000 for his medical treatment, the boy's family said he was "now able to venture outside" and had regained some movement in his legs.
Bravery, of west London, was arrested moments after the incident on the 10th storey balcony of the tourist attraction on Sunday August 4.