Police have stepped up patrols around Bridge Street car park, in Gorbals, Glasgow, following the serious sexual assault at around 2.30am yesterday.
The 35-year-old woman, wearing a full white wedding dress and veil, was walking near to Norfolk Street when she was pulled into bushes and attacked.
Detective Inspector Liz McLean, who is leading the investigation, said police are looking to speak to anyone in the area at the time.
She said: "The lady has been at a fancy dress party nearby and was crossing the car park at Bridge Street, near to the bank at Norfolk St, when she was approached by the man, pulled in to the bushes and attacked.
"We are still keen to speak to anyone who was in the area at the time who may have information that will help our investigation.
"As said, the lady had been at a fancy dress party nearby and was dressed as a bride wearing a full white wedding dress and a veil.
"Although a lot of people were no doubt dressed up for Halloween parties, I think it is very possible that someone may have seen her as she walked along the street."
The man, who is described as white, Scottish, and with dark hair and wearing dark clothing, ran off towards Eglinton Street.
The woman, who sustained cuts and bruises in the attack, made her way to the road where she stopped a passing taxi.
Two members of the public, a man and a woman, also came to her aid. They, and the taxi driver, have been traced and spoken to by officers.
Police are keen to speak to a man and woman in fancy dress who were seen on CCTV in the car park when the attack occurred.
Ms McLean added: "From CCTV, another couple, a man and woman both wearing fancy dress, are seen in the car park at the time of the attack. I would appeal to them to come forward as they might have seen something that could help us with our enquiries.
"This is a busy area with cars and buses and in particular taxis. I would ask that anyone with information contact police.
"I would like to reassure people that there are extra patrols are in the area and anyone with concerns or information can speak to these officers or call Police Scotland on the non- emergency number 101."