This is the fifth XFL player that the Steelers have signed in the past week.
Hendrix, 24, wound up going undrafted out of Pittsburgh back in May of last year. He later signed a three-year, $1.755 million contract with the Dolphins, but was waived coming out of the preseason.
Hendrix later signed on to the Dolphins practice before joining the Bears in November. He finished out the year with the Jaguars.
During his one year with the St. Louis Battlehawks, Hendrix recorded four tackles and a sack.