Durham Regional police say they were called to a residence on McCullough Drive just after 7 a.m. for an unknown trouble call.
Police found a 30-year-old Whitby man in a basement apartment suffering from "obvious signs of trauma."
The man was taken to hospital but died a short time later.
Police have not released any information on the victim's identity or the circumstances surrounding his death, other than to say it was "a violent altercation."
Police say they have not made any arrests and have not released any information on suspects in the case.