She is sometimes credited as Pamela Segall, Pamela S. Adlon and Pamela Segall Adlon. Adlon is best known for providing the voice of Bobby Hill on the animated series King of the Hill — a role for which she won an Emmy for Outstanding Voice-Over Performance in 2002. Other notable roles include Dolores Rebchuck in the 1982 feature film Grease 2, and “Girl Joey” in the 1984 teen comedy film Bad Manners (aka: Growing Pains).

In 2006, she performed as the voice of Andy in Cartoon Network's Squirrel Boy animated series, and co-starred with Louis C.K. in the now canceled HBO sitcom Lucky Louie. She starred as Marcy Runkle on Showtime's Californication and as Pamela on Louie, for which she is also a producer. Adlon voiced Pajama Sam in the cartoon games Pajama Sam In: No Need to Hide When It's Dark Outside, Pajama Sam 2: Thunder and Lightning Aren't So Frightening, Pajama Sam 3: You Are What You Eat from Your Head to Your Feet and Pajama Sam's Games to Play on Any Day.