The Daily Telegraph reported Cambridgeshire police officials said they had found no evidence to warrant further action.
Some who provided 24-hour medical care for the 62-year-old Hawking, who suffers from a motor neuron disease, alleged he had been assaulted. There had been similar allegations made four years ago.
"My investigation into these allegations has been extremely thorough and detailed," said Detective Superintendent Michael Campbell. "The purpose of this has been to establish once and for all the position with regard to Professor Hawking.
"Based on what I have learnt, I can find no evidence to substantiate any assertion that anyone has perpetrated any criminal acts against Professor Hawking."
The author of "A Brief History of Time" has been in poor health. He suffered from pneumonia, was discharged from the hospital on Feb. 7, but was re-admitted 12 days later with a recurrent chest infection.