The incident took place on the canal path between Banknock and Bonnybridge around 3:45pm on Sunday, June 20.
The man is described as white, in his 50s and bald.
At the time, he was wearing grey jogging bottoms, a grey jogging top and black trainers. He also had a black backpack and was holding a can of Tennent’s beer.
Constable Laura Newlands, from Grangemouth Police Station, said: “Clearly, this was a disturbing and upsetting incident for the woman involved, who thankfully reported the matter to police.
“We are asking the public to get in touch if they think they know who this man is, or if they were in the area around the time of the incident and may have seen the man.
“If anyone has any information that could help with our enquiries, then please contact Police Scotland on 101, quoting incident 2349 of June 20.”