The 53-year-old was between Steanard Lane and Station Road in Mirfield when her path was blocked by a group of youths on push bikes.
One of them made an offensive remark before sexually touching her. She managed to push him away and the suspects fled.
Police this afternoon released details of the incident at 1.30pm on Sunday June 11.
PC Donna Collins, of Kirklees District Police, said: "I would like to reassure local people that offences of this nature are rare and that everything is being done to investigate what took place.
"The victim is being supported by specially trained officers as the investigation progresses."
Police want to trace five youths; one is described as Asian, about 16, 5ft 7ins, stocky and wearing a light coloured top. He had short dark hair and was clean shaven. He spoke with a local accent.
Witnesses are asked to call PC Donna Collins in Kirklees District Police on 101.