The 31-year-old has spent the past week training in Perth and will provide cover for the injured Steven Anderson and the suspended Frazer Wright.
The latter has been given an extra two-match ban for comments made to the fourth official following his red card in Saturday's defeat at St Mirren.
The defender's remarks were deemed sufficient to merit a second red card and he will now sit out games against Motherwell, Hearts and Kilmarnock.
Jahic, who has 20 caps for his country, was released by Turkish top flight club Karabukspor in the summer.
Manager Tommy Wright's need for defensive cover has been exacerbated by the fact that Russell Anderson is out for up to two months with a dislocated thumb.