A man was walking his dogs on fields between Field Head Lane, Birstall, and Drighlington when he was approached by two other men.
They threatened the victim and demanded he hand over one of his French Bull Dogs dogs before grabbing at one of the dog's leads.
The victim fought back and both suspects then fled towards Drighlington.
The victim was not hurt.
Kirklees District CID would like to speak to anyone who has information about the incident, which happened at around 10am on Friday (June 10).
Both suspects were described as of middle eastern ethnicity, in their mid 20s, around 5ft 8ins tall and wearing high-visibility vests.
Anyone who saw the incident, men fitting this description or any suspicious vehicles around Field Head Lane, is asked to contact Kirklees CID on 101 referencing crime number 13220315546, or online via www.westorkshire.police.uk/101livechat
Information can also be given anonymously to the independent Crimestoppers charity on 0800 555111.