Rebecka was born in the town of Turinge, Sweden to an 18-year-old Swedish mother Kristina, and a 24-year-old Finnish father, Jyrki. Her parents divorced when she was only one year old. At the age of 9, Liljeberg began her acting career when she won a role in the series Sunes jul. Between 1993 and 1997, she became involved in amateur theatre, which she continued until landing a role in the film Närkontakt later in 1997. However, it was the following year she got her breakthrough in the Lukas Moodysson film Show Me Love (Fucking Åmål) (1998). She quit high school to make the film, which ultimately won her the 1999 Guldbagge award for best Actress, together with Alexandra Dahlström.
Rebecka stopped acting after her film Bear's Kiss (2002) and now works as a pediatrician. She lives in Stockholm.
