According to TV Line, the two actresses, who play Jenny and Vanessa respectively, will not be returning for the fifth season of the popular CW series.
An insider on the show confirmed that both actresses have been invited to return to the series on a guest star basis.
Meanwhile, Kaylee DeFer, who plays Serena's (Blake Lively) cousin Charlie, has been upgraded to a series regular.
Neither Momsen nor Szohr have been a big part of Gossip Girl's most recent season. The Pretty Reckless singer was placed on an "indefinite hiatus" in November, while the Piranha 3D star has appeared only minimally.
Project Runway star Tim Gunn, who shot a cameo for the CW series last summer, described Momsen as a "diva", stating that the actress could barely remember her lines.
Gossip Girl regular Leighton Meestor recently threatened to quit acting if she was not allowed time off to star in movies. She can be seen next in Monte Carlo opposite Selena Gomez.
Watch a clip from the Gossip Girl episode 'Shattered Bass' below: