McWilliams' career began in the mid '90s as a beta tester on games including Daggerfall, Sid Meier's Alpha Centauri, and Pirates! She served as lead designer on the real-time tactics game Full Spectrum Warrior, and then as game designer on Over the Hedge and creative director of Free Realms. She also has credits on Disney's Stitch: Experiment 626, Gears of War 4, Archangel, and The Walking Dead: Saints and Sinners.
In 2008 McWilliams was cited by Gamasutra (now Game Developer) in its list of "the 20 most vital women working in games today," and in 2021 she earned a Lifetime Achievement Award at the Game Developers Choice Awards, in recognition of "the career and achievements of a developer who has made an indelible impact on the craft of game development and games as a whole." The award recognized McWilliams' work on "award-winning adventure, social, strategy, simulation, platform, brawler, FPS, and massively multiplayer online games," as well as her regular appearances at game development conferences: "She’s an outspoken proponent of games for everyone and a fierce advocate for increased diversity on our game development teams."
Numerous developers paid tribute to McWilliams on Twitter.
"Laralyn McWilliams was a true OG of the game industry and a close friend," Romero Games studio director Brenda Romero wrote. "It took me forever to write this through tears, to figure out what I wanted to say. I remember crying at one point during one of her battles with cancer, thinking, 'You have to write what you know down! Write a book. It’s going to be lost.'
"Yet, in the window of time between her passing and this post, I’ve seen dozens and dozens of people talk about what she shared with them, what they learned, and so I suppose she left her mark on people, on games, on designs, and I think she’d like that a lot more than pages in a book that can be closed. Rest in peace, Laralyn. Thank you for all you’ve done, and thanks for being my friend."
"She was an icon, a fighter, and I got the chance to tell her once how much she meant to me, and that alone was a privilege," Marathon executive producer Carrie Gouskos wrote. "I have such profound heartache for her loved ones."
McWilliams had faced a number of serious health challenges in her life, which she was open about on social media: In December 2023 she revealed on Bluesky that she was undergoing open heart surgery due to issues arising from radiation treatment for head and neck cancer in 2012 and lung cancer in 2015.