Jadi Delgado was last seen around 5:30 p.m. on June 29 in the 1300-block of North Monitor Avenue in the city's North Austin neighborhood, police said in an alert.
DelGado is not from Chicago. She was staying with family at the time and is unfamiliar with the area, police said.
"Jadi, if you listening, at least just try to let us know something. Just text us, call us, just let us know something. That you OK. That you out there somewhere," a man said at a press conference held by Delgado's family on Monday.
Police described Delgado as a black teen with brown eyes, dark red hair and a medium complexion. She is 5 ft. 3 in. tall and weighs around 120 pounds.
Anyone with information regarding Delgado's whereabouts should call the Area North Special Victims Unit at 312-744-8266.