The incident happened around 10.40pm on August 7 on Barrows Lane, Great Eccleston, where the cat was later found with fatal injuries.
Garstang and Over Wyre police are looking to speak with a man in connection with the incident. He was walking a large, dark-coloured dog, similar in size to a setter or a retriever, that did not appear to be on a lead at the time.
A spokesman said: "We need your help to identify this male. I'm sorry for the quality of the image, but it is all we have."
Anyone with information is asked to email police on [email protected] or call 101 and quoting the reference number LC-20180807-1392.