The incident near the Old Mill Complex by Guthrie Street and Brown Street in Dundee was reported to police by a witness at 6.50pm on Sunday.
Officers said the reported attack "appeared to be an argument of some kind" but have not yet been contacted by the woman.
She is described as white, in her 30s, with brown hair, and was wearing a pale or light gold-coloured dress.
The man is described as white, aged 30-35, and was wearing a white shirt and grey trousers.
After the incident, the pair headed in the direction of West Marketgait.
Anyone with information is asked to call 101 with the reference CR/19690/19, or anonymously contact Crimestoppers on 0800 555 111.