Tulloch was born in San Diego, California, but grew up in Spain, Uruguay, and Argentina. "Bitsie" is not a contraction of Tulloch's given name, Elizabeth, but an homage to her oddly nicknamed grandfather, a World War II bomber pilot. After returning to the U.S., she went to middle and high school in Bedford, New York. Tulloch graduated magna cum laude from Harvard University with a double major in English and American Literature and Visual and Environmental Studies. Tulloch is of Scottish descent on her father's side and Spanish descent on her mother's.
Tulloch played Marilyn Sitzman, a witness to the Kennedy assassination, in the star-studded 2013 film Parkland opposite Paul Giamatti, Billy Bob Thornton, Marcia Gay Harden, Jackie Weaver, Jackie Earle Haley, and Zac Efron. The film was produced by Tom Hanks and Gary Goetzman of Playtone. It was released in November 2013 to coincide with the 50th anniversary of John F. Kennedy's assassination.
In 2012 she starred as one of the titular roles in independent film Caroline and Jackie opposite Marguerite Moreau, which she also co-produced. The film premiered at the Tribeca Film Festival in April 2012, and was released theatrically in May 2013.
Tulloch played the small role of Norma, an actress in the 1920s starring in a silent movie with a veteran actor, in the award-winning movie The Artist with Jean Dujardin, John Goodman and James Cromwell, which was released by The Weinstein Company in November 2011, and won the 2012 Academy Award for Best Picture. The cast of the movie was nominated for a Critics Choice Award for Best Ensemble Cast.
She was in Lakeview Terrace directed by Neil LaBute, opposite Samuel L. Jackson, Kerry Washington, and Patrick Wilson, and worked with Barbara Hershey on a film called Uncross the Stars. In the fall of 2009 she filmed the romantic comedy Losing Control. Tulloch voiced one of the characters, a wolf called Sweets, in Alpha and Omega, a 3-D computer animated film, which was released in September 2010. Movies Tyranny and Riding the Pine are in pre-production.
Tulloch's first acting credit was as R2-D2's "girlfriend" in R2-D2: Beneath the Dome, a mockumentary produced by George Lucas telling the life story of the fictional robot R2-D2 from the Star Wars film series. She starred as "Sally" in the premiere of Sam Forman's play, Quarterlife, which opened at the Pico Playhouse in March 2006. The Los Angeles Times wrote, "Superbly performed…the scene at the end of the play, between Sally (Bitsie Tulloch) and Jack (Clark Freeman), was heartbreaking and beautiful… The lead actress, Bitsie Tulloch, [was] absolutely brilliant."
Tulloch played the lead role in Ed Zwick and Marshall Herskovitz's drama quarterlife, which premiered on NBC in early 2008. While the series was quickly pulled and moved to Bravo, Tulloch was hailed for her performance. The Los Angeles Times wrote: "She's the best realized of the bunch... Tulloch, who plays her, seems destined to be better known." She was often compared to the 'next' Claire Danes: "Will this be the first online show to create a real star? It looks likely: The gorgeous 26-year-old Tulloch clearly possesses Danes-like smarts and magnetism."
Tulloch has appeared on television shows House, Cold Case, The West Wing, Moonlight, and Outlaw. In 2007 she filmed a role as a Dharma initiative scientist for the ABC series Lost, but her role was re-cast due to scheduling conflicts with quarterlife.
In 2009, Tulloch shot one of the 3 leads in HBO's buzzed-about comedy pilot Washingtonienne based on the book by Jessica Cutler. The pilot was produced by HBO and Sarah Jessica Parker. In early 2010 she filmed Most Likely to Succeed, a 1/2 hour comedy pilot for Imagine Entertainment through the FOX network, and a recurring role on NBC's Outlaw.
She was one of the series regulars on NBC's series Grimm, described as a dark but fantastical cop drama about a world in which characters inspired by Grimms' Fairy Tales exist. Tulloch's heritage and fluency with the Spanish language were written into the role.
In December 2014, Tulloch confirmed she is in a relationship with her Grimm co-star David Giuntoli. In July 2016, she and Giuntoli revealed they became engaged in April 2016. They married in June 2017.
During her time living and working in Portland (where her drama Grimm was filmed), Tulloch became a fan of the Portland Trail Blazers and was often seen attending games with her co-stars. Tulloch is fluent in English and Spanish.
In early 2012, Tulloch was nominated by the Broadcast Film Critics Association Awards, commonly called the Critics' Choice Awards, for Best Ensemble Cast for The Artist.
Tulloch was nominated for a 28th Annual LA Weekly Theater Award for her performance in Sam Forman's play, Quarterlife (March 2007). Quarterlife was an experimental sequence of 20+ episodes which were originally intended to be released only on the internet, but its success led it to being picked up by NBC.