29-year-old Andrew Hutchinson, who worked at John Radcliffe Hospital in Oxford, also admitted spying on women at a leisure centre and sexually assaulting women at a music festival.
His victims were aged between 10 and 35, the BBC reported.
Hutchinson sexually assaulted four unconscious women, in curtained areas in the hospital's A&E department and at Wilderness music festival.
He also used a camera to spy on women and children at the White Horse Leisure Centre in Abingdon.
Hutchinson admitted all 27 counts against him at at Oxford Crown Court.
He was sacked by the hospital after he was arrested.
He was arrested by Thames Valley Police on suspicion of voyeurism offences at the leisure centre in November 2013 and charged in December last year.
Police also found images on devices, including a mobile phone, a memory stick and a camera, seized from Hutchinson which brought to light other incidents.
He has been remanded for sentencing on April 27.
Police said all identifiable victims had been contacted and given support.
"I have no doubt that Hutchinson would have continued to offend had he not been arrested," he said.
