Ostovich faced Karine Gevorgyan on December 1, 2017, at The Ultimate Fighter 26 Finale.
She won the fight via armbar submission in the first round.

Ostovich faced Montana De La Rosa  on July 6, 2018, at The Ultimate Fighter 27 Finale.
She lost the fight via rear-naked choke in round three.

Ostovich was scheduled to face Paige VanZant on January 19, 2019, at UFC on ESPN+ 1.
It was reported on November 18, 2018, that Ostovich was violently assaulted, sustaining a broken orbital bone and other injuries, and due to the injuries she sustained, she pulled out from the fight against VanZant.
On November 27, the bout between Ostovich and VanZant was confirmed to push through on January 19, 2019, after Ostovich was cleared to fight by her doctor.
Ostovich lost the fight by submission via armbar in the second round.

Ostovich was scheduled to face Veronica Macedo on August 10, 2019 at UFC on ESPN+ 14, but Ostovich was replaced by Polyana Viana for unknown reasons.

Ostovich was scheduled to face Shana Dobson at UFC Fight Night 168 in Auckland, New Zealand on February 23, 2020 at UFC Fight Night 168.
However, Ostovich was removed from the bout due to testing positive for ostarine, and she was replaced by Priscila Cachoeira.
On June 18, it was announced that Ostovich had accepted a USADA suspension for one year due to testing positive for ostarine, retroactive to January 3, 2020.

Ostovich tested positive for Ostarine and GW1516 on January 3, 2020 and she was suspended by USADA for eight months.
The prohibited substance were found in her supplement were not listed on the supplement label.
Ostovich faced Karine Gevorgyan on December 1, 2017, at The Ultimate Fighter 26 Finale. She won the fight via armbar submission in the first round.
Ostovich faced Montana De La Rosa  on July 6, 2018, at The Ultimate Fighter 27 Finale. She lost the fight via rear-naked choke in round three.
Ostovich was scheduled to face Paige VanZant on January 19, 2019, at UFC on ESPN+ 1. It was reported on November 18, 2018, that Ostovich was violently assaulted, sustaining a broken orbital bone and other injuries, and due to the injuries she sustained, she pulled out from the fight against VanZant. On November 27, the bout between Ostovich and VanZant was confirmed to push through on January 19, 2019, after Ostovich was cleared to fight by her doctor. Ostovich lost the fight by submission via armbar in the second round.
Ostovich was scheduled to face Veronica Macedo on August 10, 2019 at UFC on ESPN+ 14, but Ostovich was replaced by Polyana Viana for unknown reasons.
Ostovich was scheduled to face Shana Dobson at UFC Fight Night 168 in Auckland, New Zealand on February 23, 2020 at UFC Fight Night 168. However, Ostovich was removed from the bout due to testing positive for ostarine, and she was replaced by Priscila Cachoeira. On June 18, it was announced that Ostovich had accepted a USADA suspension for one year due to testing positive for ostarine, retroactive to January 3, 2020.
Ostovich tested positive for Ostarine and GW1516 on January 3, 2020 and she was suspended by USADA for eight months. The prohibited substance were found in her supplement were not listed on the supplement label.
Rachael Ostovich