Griffin will be joined by Rivers' daughter and FP producer Melissa Rivers, as well as co-hosts Giuliana Rancic and Kelly Osbourne. It's unclear as to whether fellow co-host George Kotsiopoulos will stay on as well, reported TMZ online.
The show will no longer be aired on a weekly basis, but will air only during awards season and other special occasions as event programming.
"Joan has always given her blessing to Kathy and that she wanted Kathy to be her successor," a source said.
"They talked about it many times. They have such a similar sense of humour and were the best of friends. Joan would have loved seeing Kathy on Fashion Police and she would have definitely approved."