In 1981, Kennedy co-founded the production company Amblin Entertainment with Steven Spielberg and her eventual husband Frank Marshall.

Her twin sister, Connie, formerly a location manager in British Columbia, Canada, is now the executive producer of the Virtual Production company Profile Studios.

[citation needed] Her other sister is Dana Middleton-Silberstein, a television host and anchor, and press secretary/communications director for former Governor Gary Locke (D-WA).

[5] After her employment with KCST, she produced a local talk show entitled You're On for the station for four years before moving to Los Angeles.

In Los Angeles, Kennedy secured her first film production job working as an assistant to John Milius, who at the time was executive producer of Spielberg's 1941 (1979).

While working under Milius during the production of 1941, Kennedy caught the attention of Steven Spielberg,[7] who stated in 2015:She was horrible at taking notes... but what she did know how to do was interrupt somebody in midsentence.

[9] She also produced Indiana Jones and the Temple of Doom (1984) with George Lucas and Marshall, and appeared in the film's opening sequence as a dancer.

With Amblin, she produced the Back to the Future trilogy, collaborating with such directors as Martin Scorsese, Robert Zemeckis, Barry Levinson, and Clint Eastwood.

Marshall and Kennedy were producers for the US versions of two Studio Ghibli animated features Ponyo (2009) and The Secret World of Arrietty (2012).

[24][25] That same year Kennedy was appointed an honorary commander of the Order of the British Empire, for services to film production in the United Kingdom.

[32] In 2007, Kennedy was the first recipient of Women in Film's Paltrow Mentorship Award, for showing extraordinary commitment to mentoring and supporting the next generation of filmmakers and executives.