Denise Daniels said the animated film, featuring colour-coded characters representing individual human emotions, mirrors a children's program called The Moodsters hat she conceived and pitched to Disney every year from 2005 to 2009.
In a complaint filed in the Los Angeles federal court, Ms Daniels said she had an 'implied-in-fact' contract with Disney requiring that she be paid from box office, DVD, Blu-Ray, iTunes and merchandise revenue from Inside Out.
The film has grossed more than $US850 million worldwide since its June 2015 release.
Ms Daniels said this "extreme success" was not possible without her work, and that Disney should pay her because it is "custom and common in the entertainment industry".
A Disney spokesman, however, said Inside Out was an original Pixar creation.
"We look forward to vigorously defending against this lawsuit in court," the spokesman said.
Inside Out follows 11-year-old Riley, voiced by Kaitlyn Dias, as she tries to cope with her family's move to San Francisco from Minnesota.
It shows her dealing with personifications of five emotions: Joy (yellow), Sadness (blue), Fear (purple), Anger (red) and Disgust (green), voiced by Amy Poehler, Phyllis Smith, Bill Hader, Lewis Black and Mindy Kaling.
Ms Daniels said this resembled The Moodsters, in which characters also had assigned colours: Happiness (yellow), Sadness (blue), Fear (green), Anger (red) and Love (pink).
According to her complaint, Inside Out director Pete Docter, former Disney chief financial officer Thomas Staggs and several other Disney executives had access to her pitch.
No individuals were named as defendants.
Ronald Schutz, a lawyer for Ms Daniels, declined to comment and Ms Daniels was unavailable to comment.
The lawsuit is at least the second in three months accusing Disney of stealing a concept for a blockbuster film.
In March, Hollywood screenwriter Gary Goldman, whose credits include the Arnold Schwarzenegger film Total Recall, sued Disney for allegedly copying its Oscar-winning animated film Zootopia from his work.
Disney has denied wrongdoing and asked a federal judge to dismiss Mr Goldman's complaint.