Versatile Scarlets back McNicholl and Cardiff Blues centre Halaholo are among five uncapped players selected by new head coach Pivac for the clash at the Principality Stadium.
Taine Basham, Shane Lewis-Hughes and Ashton Hewitt will also be hoping to don the red shirt for the first time against a Baa-baas side coached by former Wales boss Warren Gatland.
Captain Alun-Wyn Jones is among the absentees due to injury, while England-based duo Dan Biggar and Rhys Carre are unavailable as the game falls outside the Test window.
Pivac excited to get going with Wales.... pic.twitter.com/RlRpunTmm1
— Welsh Rugby Union (@WelshRugbyUnion) November 19, 2019
Pivac said: "It is great to get the squad announced and get the ball rolling on our first meet-up and first fixture next week.
"This Barbarians game is a great chance for us as a new squad and management to get together and to set the scene for what we are looking to do. Having this opportunity ahead of tournament rugby in the Six Nations is ideal for us.
"It is also a great chance for some players to really put their hand up and show what they are about and take to the field in front of a big crowd at home.
"We will be bringing a few additional players in to train with the squad during the week, just to see them in the environment and will also be bringing some of the injured players in for some of the scene setting style sessions."
Forwards: Elliot Dee, Ryan Elias, Ken Owens, Rob Evans, Wyn Jones, Nicky Smith, Leon Brown, Samson Lee, Dillon Lewis, Jake Ball, Adam Beard, Bradley Davies, Seb Davies, Taine Basham, Ollie Griffiths, Shane Lewis-Hughes, Ross Moriarty, Aaron Shingler, Justin Tipuric, Aaron Wainwright.
Backs: Aled Davies, Gareth Davies, Tomos Williams, Sam Davies, Jarrod Evans, Willis Halaholo, Hadleigh Parkes, Owen Watkin, Owen Lane, Josh Adams, Steff Evans, Ashton Hewitt, Johnny McNicholl, Hallam Amos, Leigh Halfpenny.