Sifiso Vilakazi scored for Free State Stars and John Maduka scored for Celtic.
Celtic threatened first when Moses Spandeel had an effort saved by Kennedy Mweene in the seventh minute.
Ruben Cloete should have put Ea Lla Koto ahead in the 26th minute when he found himself in a promising position inside the area, but Celtic keeper Shuaib Walters made a good save to deny the midfielder.
Lebogang Mothibantwa had a header saved by Mweene on the stroke of halftime, with the remaining goalless at the break.
Celtic dominated the opening stages of the second half with Maduka and Mothibantwa going close.
Stars took the lead in the 53rd minute when Vilakazi struck with a low shot from just outside the area.
Mweene again denied Celtic from scoring in the 64th minute when he saved a header from Timothy Batabaire.
However, Celtic deservedly leveled matters with a shot by Maduka in the 77th minute following a cross by Didier Mbendje.
Sipho Nkosi almost sealed the win for Stars a minute from the end when he received the ball inside the area, but his shot was superbly saved by Walters.
Celtic are away to AmaZulu on September 16, while Free State Stars host Black Leopards.