The X-Men spin-off, starring Ryan Reynolds, is one of five films up for the guild's adapted screenplay prize.
Oscar-tipped titles La La Land and Moonlight are among those in contention for its original screenplay award.
Last year both Spotlight and The Big Short went on to win screenplay Oscars after being recognised by the WGA.
Deadpool's competition includes Denzel Washington's film version of August Wilson's stage play Fences.
