Having had walk-on roles in her mother's television series The Lucy Show, Arnaz made her acting debut in a continuing role in the series Here's Lucy from 1968 to 1974. She played Kim Carter, the daughter of the eponymous Lucy—who was played by Arnaz's real-life mother, Lucille Ball.
Arnaz also had a short-lived series of her own, The Lucie Arnaz Show, on CBS in 1985. The reviewer for The New York Times described the show as "the always ingratiating Miss Arnaz as a psychologist who not only writes an advice column but also takes calls from listeners on her own radio program."
She won an Emmy Award , for Outstanding Informational Special, in 1993 for her documentary about her parents, Lucy and Desi: A Home Movie.
She toured in Pippin in 2014, playing the part of "Berthe", the title character's grandmother. She appeared on Broadway in Pippin, from October 9, 2014 to November 9, 2014
In 2010, Arnaz performed in (along with Raul Esparza and Valarie Pettiford) and directed "Babalu: A Celebration of the Music of Desi Arnaz and his Orchestra". There was a Miami, Florida performance in July 2010.
In October 2008, Arnaz and long-time family friend, Hollywood columnist and Turner Classic Movies host Robert Osborne participated in a tribute to Arnaz's mother, Lucille Ball, at The Paley Center For Media in New York City. (The Paley Center announcement: Tuesday, October 28; 6:30 pm; Panelist: Lucie Arnaz; Moderator: Robert Osborne, Host, Turner Classic Movies.) The program, "Lucie and Lucy: Lucie Arnaz Shares Treasures From The Family Video Collection", included a discussion between Osborne and Arnaz about Ball, and also focused on Ball's last long-running series, Here's Lucy (which was celebrating its 40th anniversary) as well as several of Ball's television specials and guest appearances during the 1970s, which Arnaz had recently donated to The Paley Center for Media.
On July 17, 2010, Heritage Auction Galleries planned to auction off some items that belonged to Lucille Ball. Arnaz had gone to court to block the auction of love letters from Ball to her second husband, Gary Morton, as well as photos and awards, which Arnaz claims are hers. Morton's third wife, Susan McAllister Morton, had sued Arnaz for the right to conduct the auction. A judge agreed with Arnaz, but charged too high a bond, so the auction went on but the auction house agreed to return lifetime achievement awards to Arnaz.
She appeared live on stage in Jamestown, New York at the Reg Lenna Palace Civic Center on August 3, 2012 to promote the Lucille Ball Festival of New Comedy in which new comedians are invited to perform. She gave tribute to both her parents, and expressed a desire to further expand the Festival of New Comedy and expand the Jamestown New York Lucy Fest. She gave the history behind the Lucy-Desi Museum and Lucy-Desi Playhouse, and the 2011 birthday centenary for Lucille Ball (which was recorded in the Guinness Book of World records for the highest number of people dressed like Lucille Ball in one place at one time), and announced intent to start utilizing the recently renovated Jamestown train station to further the mission and vision of the Lucille Ball Festival of New Comedy. Lucie Arnaz praised and appeared on stage with the new executive director of The Lucille Ball Desi Arnaz Center and applauded her work and dedication to the Festival.