Sussex Police is issuing a warning to dog owners in Mile Oak, after reports that lumps of meat laced with poison were found in the area.
Letters are being sent to residents of Sidehill Drive where the contaminated meat was found at the entrance of a grassed area, police said.
A police statement said: "We are investigating a report of a dog needing to go to the vet after eating the contaminated meat. Thankfully the dog was OK.
"Local residents are aware that this is a popular dog walking area and we urge them to be vigilant and report any suspicious behaviour.
"If they see any similar pieces of meat we advise them to pick them up and remove them and report it to police. We are investigating the circumstances and take any report seriously."
Mile Oak resident Ali Dolloso posted a picture of a sign put up in the Mile Oak area on Facebook, warning residents about the incident.
She said: "This is large park off Mileoak Road. A warning to everyone in Brighton, Hove, Portslade, Southwick, Shoreham. I am very worried as this is just behind my house and my cats play there, be careful if you are taking your dog around and please spread the word this person is around Brighton, Hove and Portslade. Prob Southwick/Shoreham too!!"
If you have any information about the incident, contact police on 101 or report online with the reference 47170075899.