The 44-year-old was grabbed from behind by the man as she walked along a path off Gleethorpe Road, Grimsby at about 6am this morning (Tuesday)
She sustained bruising to her arm but was not seriously injured.
A spokesperson for Humberside Police said: "The intentions of the man are not known, however the woman managed to struggle free from the man’s grasp walking quickly away.
"The victim described the man as being white with dark brown curly hair. She believes she saw the man staggering along a nearby path shortly before the assault took place."
Anyone with information is asked to contact Humberside Police on 101.