Ashley Grundy and Steven Robinson carried out the depraved act as revenge after an argument in a pub.
The barbaric pair were in the Barons Rest pub in Astley Village when they got into a dispute with another customer on May 19, 2018.
In the early hours of the following morning, the pair drove to the victim’s address in Whittle-le-Woods before stealing their pet Yorkshire Terrier Bailey.
They then drove back to the Barons Rest pub where they decapitated the dog.
The pair went on to leave Bailey’s head on the handle of an address in Astley Village – where the victim’s mother lived with her child.
Police launched an investigation following the incident and carried out extensive enquiries to bring the pair to justice.
An extensive CCTV trawl showed Robinson discarding an item – which had been wrapped in a car mat – into a bush near the Barons Rest pub.
The item was later found to be Bailey's decapitated body.
Grundy, 31, of Preston Street, Kirkham, and Steven Robinson, 39, Lancaster, were charged with criminal damage and outraging public decency.
They were sentenced to 19 months in jail after appearing at Preston Crown Court on Friday (May 13).
Sgt Paul Harrison, who led the investigation, said: “This was a lengthy investigation which involved a number of officers.
“Officers sat through hours of CCTV and had to go through distressing incidents to compare the DNA from Bailey’s head and carcass to the DNA of the blood found in and on the vehicle that Grundy and Robinson were using.
“I’d like to thank all the officers involved who worked tirelessly to bring this investigation to a conclusion.
“I now hope that this can give some closure to the victim who lost a beloved pet due to the barbaric act of these two individuals.”
The Crown Prosecutor described the incident as an act of revenge and intimidation which was intended to cause maximum fear to the victims.