The 39-year-old victim was walking along Barnsley Road in Fir Vale when a silver car with three men inside pulled up and one of them hurled a liquid at her that police believe may have contained harmful agents.
A South Yorkshire Police spokesperson said: "Officers are investigating following an incident in the Fir Vale area of Sheffield in which a woman was sprayed with a possible noxious substance.
"One of the men is said to have shouted the woman before spraying a liquid in her face. The woman was not seriously injured."
The incident happened yesterday evening at 7.10pm.
Anyone with information is asked to call 101 quoting incident number 974 of 3 August 2017.