The pensioner across the man in her home on Hawkstone Avenue, Guiseley, at around 2pm on Wednesday October 31.
He pushed past the pensioner while making his getaway causing her to fall over and injure her head and hip.
He stole a small gold chain with a gold cross, which is of sentimental value to the victim.
He is described as white, around 20-years-old, around 5ft 9ins, slim, with short, mousey-coloured hair. He was wearing a ‘brownish’ Puffa jacket and possibly grey jogging bottoms.
PC Jim Lee, of Leeds District Crime Team, said: “Thankfully the victim was not seriously injured but being confronted by an intruder in your home would be a shocking incident for anyone, let alone for a woman in her late 80s.
“I would appeal to anyone with information which could help our ongoing enquiries into this robbery to please get in contact.”
Call 101 or using the 101 Live Chat facility on the West Yorkshire Police website, quoting crime reference 13180546035.
Information can also be given anonymously to independent charity Crimestoppers on 0800 555 111.