The attack is believed to have taken place on or near Queens Road between 12pm and 2pm on Friday July 9.
West Yorkshire Police were called to Alabama Street by the ambulance service at 4.30pm, where the victim had flagged down a neighbour for help.
The man had serious head injuries and told officers he had been a victim of an assault earlier in the day.
He was taken to hospital, where he remains in a serious but stable condition.
The Homicide and Major Enquiry Team (HMET) is investigating the attack and would like to speak to anyone who may have witnessed it.
Detective Chief Inspector Sharron Kaye of HMET said: "This is a serious incident in which the victim has been attacked and left with significant head injuries.
“We are investigating what took place and believe the victim was subject to a serious assault on or near to Queens Road.
“He was then able to get home to a neighbour who summoned help.
“Officers are investigating the circumstances of this attack and very much want to hear from anyone who saw or has mobile phone or any other footage of what occurred.
“Anyone who can assist our enquiries is asked to contact Calderdale District CID on 101 referencing crime number 13210345652.
“Information can also be given online at www.westyorkshire.police.uk/101livechat or anonymously to the independent Crimestoppers charity on 0800 555 111.