Police said the man was seen with a small white dog near where a 27-year-old woman was sexually assaulted.
The dog walker was in Glasgow Green at about 11.30pm on Saturday, April 19.
The woman was attacked as she walked into the park from Saltmarket, as reported in the Evening Times last week.
A police spokeswoman said: "The dog walker may have passed the attacker or victim and we could encourage him to contact us."
Police have also appealed for another man who may have information that can help find the attacker.
The assault happened when the woman was approached from behind by a man who pushed her to the ground before she managed to break free and escape.
She later passed a man while crossing a footbridge from Glasgow Green into Adelphi Street, Gorbals.
Police want to speak to the man on the bridge and anyone else who was in the park at the time.
Detective Inspector Diane Caldwell said: "If you were in the area at the time please contact us. You may have noticed something that could prove vital in our investigation."
The victim, who was on her way home from work, did not need hospital treatment but was left badly shaken by her ordeal.
Her attacker was white, about 5ft 8in, with short dark hair.
Officers have been reviewing CCTV in an attempt to find potential witnesses.
Forensic teams also examined parts of Glasgow Green.
Anyone who has information is asked to contact police at London Road on 101.