Portia Reiners began performing when she was seven years old in her first role as Oliver Twist in "Oliver." She continued acting in theater, portraying a large variety of characters until she was ten when she signed with Abrams Artists Agency. She made her first television appearance in the same year on All My Children (1970) and continued building her resume, performing in plays including; "More Lies About Jerzy" as Kasia opposite Jared Harris and Jenny Litnov in Wendy Kesselmans "The Notebook" at The Mcginn and Cazale and films such as The Gray Zone (2001) as the voice of the Young Girl and as Jenny in HBO's Iron Jawed Angels (2004).

In 2006, she stepped in for Leven Rambin, playing Lily Montgomery on All My Children (1970) and worked throughout the summer of 2006 on As the World Turns (1956) as Ada Dunne. In the fall of 2006, Portia was cast as Britney Jennings on One Life to Live (1968).