Alex MacNicoll

He was born and raised in Hunterdon County, New Jersey. He discovered acting during his senior year of high school through a television and media class and by making short films in his English class, later switching to a theater major at DeSales University in Center Valley, Pennsylvania. After graduating, MacNicoll moved to Los Angeles in 2013, working multiple jobs simultaneously including as a server, bartender, dog walker, and security guard while pursuing acting.

His on-screen debut came in 2013 with the television series Auditions from Hell. He gained early recognition with a recurring role as Colton on Amazon Prime Video's comedy-drama Transparent, appearing in five episodes in season two."

His early film work included the Disney sports drama McFarland, USA (2015) as Fitz Mitchell, which was his first SAG job, the football drama My All American (2015) as Mike Campbell, and the science-fiction film The 5th Wave (2016) as Flintstone. On television, he appeared in episodes of Criminal Minds, The Fosters, Bones, and Rizzoli & Isles, before landing a recurring role as Peter Standall on Netflix's 13 Reasons Why (2017–2020). In 2018, he appeared in the science-fiction film A.X.L. as Sam Fontaine, a rival motocross racer.

In 2019, MacNicoll was cast as Luke Holbrook, a former high school quarterback in a relationship with Helena, played by Natasha Liu Bordizzo, in the Netflix mystery series The Society. Created by Christopher Keyser and released on May 10, 2019, the series follows teenagers who return from a canceled school trip to find their Connecticut town completely cut off from the outside world. The series was renewed for a second season in July 2019 but was cancelled on August 21, 2020, due to complications arising from the COVID-19 pandemic.

Deadline Hollywood reported in 2023 that he had been cast as series regular Dr. Van Markus alongside Zachary Quinto in the NBC medical drama pilot Brilliant Minds. The series inspired by the work of neurologist Oliver Sacks premiered on NBC on September 23, 2024. He plays a medical intern diagnosed with Mirror-Touch Synesthesia, a rare condition causing him to physically experience the sensations of those around him. To prepare, MacNicoll researched the experience of Joel Salinas, a neurologist at NYU Langone Health who lives with the condition, telling NBC Insider: "It was just all about reading up on that and learning about his experience and trying to apply it to my own life."

The series was renewed for a second season, which premiered on September 22, 2025.

In 2025, Deadline Hollywood reported his casting in the indie horror film Sweetest Day. In March 2026, Deadline reported that he had been cast in Change the Prophecy, a short film from writer and director Lindsay Grossman serving as a television proof-of-concept.