They join previous-announced cast members Darren Criss, Jeremy Pope and David Corenswet, who are all executive producing the Netflix series as well, reports deadline.com.
Few details about the show are known, which Murphy calls "a love letter to the Golden Age of Tinseltown". It received a straight-to-series order at the streaming giant.
It is believed to be set in the 1940s and is about three lead characters played by Pope, Criss and Corenswet.
McDermott will play Ernie; Weaving will portray Claire; Parsons will play Henry Wilson; Apatow will portray Henrietta; Mantello will play Dick; Harrier will play Camille; and Picking will play actor Rock Hudson.
Murphy co-created the series with frequent collaborator Ian Brennan. Principal photography got underway earlier this year. It is slated to debut on Netflix in May 2020.
"Hollywood" is Murphy's third show for Netflix following "The Politician" and "Ratched", and the first under his mega overall deal with the streamer.
This marks Murphy's latest collaboration with McDermott who starred in the very first installment of "American Horror Story" and can be seen in Murphy's series "The Politician".
Weaving can be seen as the lead in thriller "Ready or Not", and she also stars opposite Daniel Radcliffe in action comedy "Guns Akimbo".
Parsons co-starred in Murphy's movie "The Normal Heart", earning an Emmy nomination. "The Big Bang Theory" star is also reprising his role from Murphy's Broadway production of "The Boys In the Band" in Murphy's Netflix film adaptation.
( With inputs from IANS )