Eve's acting career began in television in 1966. In 1967, she appeared on The Virginian as a happy go lucky child who loved apple pie. In 1968, she played Eve Bowers, a terminally ill classmate of Buffy and Jody in the Family Affair episode Christmas Came a Little Early.

In the 1969–74 ABC hit series The Brady Bunch, Plumb portrayed Jan Brady, one of three sisters. Themes of episodes where she was featured included her character's insecurity over wearing glasses, being a middle child, embarrassment over not having a boyfriend, jealousy of her older sister, Marcia, and concerns over her future appearance.

In 1976, Plumb appeared in the made-for-television movie Dawn: Portrait of a Teenage Runaway, and joined the LA-based Groundlings improv comedy troupe. In 1978 appeared in an episode of The Love Boat. Plumb was the only original cast member who chose not to participate in the 1976–77 Brady Bunch Hour variety show. During production of the show, Plumb appeared as Beth in NBC productions of Little Women, both a TV movie and a short-lived series.

Plumb worked steadily on stage and in television roles through the 1990s. She appeared in the Saturday morning sitcom Fudge (1995–1997) as the title character's mother, Mrs. Ann Hatcher, and in the movie Fudge-A-Mania (1997). She was also the original Pam Burkhart on That '70s Show (only seen in episode 6 "The Keg"). In addition, Plumb made a cameo appearance in the 1988 movie I'm Gonna Git You Sucka.

She appeared as one of the "Strangers" on the December 18, 2006 premiere episode of the NBC game show Identity. She was introduced at the start of the show as "Eve Plumb from The Brady Bunch." The contestant incorrectly selected her as an "Academy Award Winner," despite host Penn Jillette cautioning the contestant that The Brady Bunch was a TV show and the Academy Awards were for films. Plumb's actual identity was a painter.

In August 2008, she appeared on an episode of Days of our Lives.

In addition to acting, she has been painting for over 20 years and is now enjoying success being carried by select galleries across the country. Utilizing oil on canvas her focus is 'spontaneous still life'. Eve's Art Website

In the 1980s, Plumb chose to participate in several Brady made-for-TV movies projects, including The Brady Girls Get Married which led to The Brady Brides, a short-lived sitcom in which she was a co-lead. She also appeared in A Very Brady Christmas 1988 TV-movie and the 1990 dramedy series The Bradys. Plumb's character Jan had marital problems in A Very Brady Christmas, and fertility problems in The Bradys which led to her and her husband Phillip Covington III to adopt a Chinese girl named Patty.

In an article published by the Chicago Tribune in the 1990s on The Real Live Brady Bunch stage spoof, Plumb participated in a performance (albeit not as "Jan" but as "Tammy" the Johnny Bravo record producer) and was met by enthusiastic fans who asked "What was your favorite episode?" Plumb replied somewhat jokingly "The last one". Seeing their disappointment, she modified her answer by saying "The Grand Canyon episode was kind of cool." Plumb has since stated that she and her Brady costars have an unspoken agreement to always be courteous and polite to fans of The Brady Bunch.

In a TV Land special The Brady Bunch 35th Anniversary Reunion Special: Still Brady after All These Years, broadcast on September 29, 2004, Plumb stated that she had never seen The Brady Bunch Movie. When asked to give the audience an update on her life today, she stated that she was "still auditioning".