"I’m incredibly proud of Jack," the Partridge Family star shared. "Even coming from a family of singers, I believe his natural soulfulness and incredible range make him a standout."
Jack, who is the nephew of singer David Cassidy and the son of Broadway actor Patrick Cassidy, performed a powerful cover of Joan Osborne's "One of Us" while playing the piano, and the soulful rendition earned him a place on Alicia Keys' team.
"We're all eager to watch his rise on The Voice and are grateful to Alicia Keys for taking him under her wing," Jones added.
On Monday's The Voice, Jack opened up about coming from a famous family in a pre-recorded package before his performance, and admitted that he is looking at his time on the show as an opportunity to "really carry on the family legacy."
Jones also sat down for the package, where she said that, at first, she "was not very happy with him going into show business."