The incident happened at 7.30am on Monday, September 26, as the girl walked her dog along Sheffield Street, close to the junction of Frodingham Road.
She was approached from behind by a man who indecently exposed himself and indecently touched her.
Detective Chief Inspector Mark Kelk said: “We are keen to speak to both men in connection with this incident, which we are treating very seriously and left the victim - understandably - very shaken.
“We are continuing to follow up a number of lines of enquiry and are undertaking house to house enquiries to identify potential witnesses.
“I would like to appeal to all those living or working in the area who believe they may have seen either of the men – or are able to identify them – to come forward.”
Anyone with information is asked to call 101, quoting log number 111 of September 26.