During the last few months, farmers on the Angle Peninsula have reported problems with fences being cut, field gates being left open and cattle being worried.
The incidents have been happening late at night and it is believed the visitors are hunting, using lamps and dogs.
Pembroke Neighbourhood Policing Team are asking all residents in this area to be vigilant and report any sightings of such activities to police, the landowner or farmers.
People are being asked to pay particular attention to any vehicles left in unusual locations or unfamiliar vehicles travelling about after dark.
Anyone with information can contact Pembroke Dock Police Station on 0845 330 2000 or Crimestoppers on 0800 555 111