The 63-year-old, who uses a walking stick, was approached by a stranger while trying to cross the junction of Lord Street and Kirkgate in Huddersfield town centre after leaving the King Street Mission.
The stranger took hold of the victim’s arm but while they were in the road the 63-year-old stumbled and fell.
Whilst the victim was on the floor the suspect stole his wallet and a gold bracelet before helping him to his feet and across the road, where the suspect met with a woman.
Both left the victim and walked away, up Kirkgate.
The man was about 5ft 3ins, aged around 25 and was wearing a white baseball cap and white jacket. The woman is Asian, aged around 30. She wore an ankle-length white dress and had black hair.
The incident happened at around 2.15pm on Wednesday.
Det Con Pete Usher said: “This was a cynical and reprehensible offence in which an obviously vulnerable man has been targeted and then had his property taken.”