A woman walking her dogs with her partner on Sydney's lower north shore has been abused and bashed in an unprovoked and possibly racially motivated attack.

A 26-year-old woman and her 29-year-old partner left their Mosman home on Monday night to walk their dogs.

Just after 11pm, they were walking along Glover Street when the couple noticed a man on the other side of the road calling out to them.

"There is a possibility it's racial abuse but we haven't had a chance to talk to the victim yet as she is in hospital," Detective Chief Inspector Craig Thorpe said.

The man, who was not known to the couple, then crossed the road and allegedly pushed the 29-year-old woman, who is Asian, before head-butting her.