Janet Healy started her career in live-action films, working with directors Stanley Kramer, Hal Ashby and Sam Peckinpah. She worked with Steven Spielberg on Close Encounters of the Third Kind and 1941, serving as Associate Producer on the latter.

She then joined George Lucas' visual effects company, Industrial Light & Magic (ILM), as a Co-Head of Production. At ILM, Janet produced some of the era's most groundbreaking visual effects work, including the Academy Award®-winning visual effects for Terminator 2: Judgment Day and Jurassic Park. She was instrumental in leading the industry transition from reliance on photo-chemical and in-camera processes to the use of the digital 2D and 3D techniques that are common place in visual effects today. During those years at ILM she was also the Visual Effects Producer for Ghostbusters II, Joe Versus the Volcano, and Willow.

In 1995 she joined Walt Disney Feature Animation as the Head of Digital Production and oversaw the CG work on the films Tarzan, Dinosaur and Mulan. She moved to DreamWorks Animation a to serve as Head of Production for several years and was a Producer on Shark Tale.

In 2008, Janet joined Chris Meledandri at Illumination Entertainment and Universal Pictures. Along with Chris, Janet is the Producer of Despicable Me, The Lorax, Despicable Me 2, The Minions, The Secret Life of Pets, Sing, Despicable Me 3, The Grinch, The Secret life of Pets 2, Sing 2, and Minions:The Rise of Gru.

Janet is a member of the New Media Council of the Producers Guild of America and a Founding Member of the Visual Effects Society. She has served as a member of the Board of Directors and as an Executive Board member of those organizations respectively. In 2014 she was awarded the Visual Effects Society's highest honor, The Founder's Award, for her contributions to the industry and to that organization. She is also a member of The Academy of Motion Picture Arts and Sciences. As of 2022, the films Janet has produced have earned more than $ 8 billion worldwide.

In 2015 she was honored to be a recipient of the Chevalier of the Order of Arts and Letters by the French Ministry of Culture, and she is also a Dame of Saint-Émilion, France.