The woman was at home on Holts Lane, Poulton at 11am on Tuesday when the robber walked into her home.
The 36-year-old told police the raider put his hand over her mouth before stealing her watch, ring, bracelet and other jewellery.
He then left heading towards Poulton Industrial Estate.
Officers are carrying out house to house enquiries and looking for CCTV.
The suspect is described as a white male, in his 30s, 6ft 2ins tall and ofmuscular build.
He was wearing a black bomber jacket and dark trousers.
Det Insp Gareth Willis, of Blackpool CID, said: “I would appeal to anyone who may have seen someone acting suspiciously to get in touch.
“I’d also advise people to take basic security measures such as keeping doors and windows locked.”
Anyone with information should contact police on 101 quoting log number 0383 of today (December 1st) or Crimestoppers on 0800 555 111.