After full time, Pennington was named the winner by unanimous decision, 29-28, 29-28, 29-28.
Ahead of the meeting, Kianzad, who competes in bantamweight, had four straight UFC wins behind him.
She has attended a total of seven meetings within the organization.
Raquel Pennington was suspended for six months in November last year after using illicit drugs.
It was she who reported the use when she realized that medicines she had been prescribed contained illicit substances.
The meeting with Kianzad was her first in the UFC after the suspension.