The family of Gerald Serroul, of Sydney Mines, says the 74-year-old was suffering from Alzheimer's disease and had been a patient at the Northside General Hospital since his wife, Helen, died of cancer in August.
The Cape Breton Post reports Serroul fell from a second-storey window at the hospital on Sunday.
The man's granddaughter, Lisa Capstick, told the newspaper the family has hired a lawyer.
Lynn Gilbert, a spokeswoman for the Cape Breton District Health Authority, confirmed an internal review has started but would not discuss any details, only saying an "unplanned and unfortunate experience" had taken place.
"As part of our investigation, we'll be looking at the timeline of events, any processes or procedures in place, structural issues and anything else that could've factored into the event," she said in a statement to CBC News.
"We'll also be looking at if there is anything we can do to prevent events like this from happening again."