The man, who is believed to have been in his 40s, was found unconscious near to a petrol station at Serpentine Road, Cleckheaton, in the early hours of Wednesday morning.
The man was pronounced dead a short while later.
Residents woke to find the road cordoned off and the sight of a forensics tent.
A spokeswoman for West Yorkshire Police said: "Police were called at 2.50am this morning to Serpentine Road, Cleckheaton, to a report of an unconscious man on the pavement. Paramedics also attended at the scene and the man was pronounced deceased a short time later.
"The body is yet to be formally identified but is believed to be a man in his 40s.
"The death is being treated as unexplained pending a post-mortem examination, but at this time there are no suspicious circumstances to the death."