Kertesz was born in Ramat HaSharon, Israel, to a family of Jewish background. Her father, Gabriel Kertesz, is an architect who works on preserving historical neighborhoods and landmarks. He immigrated to Israel from Transylvania, Romania, when he was nine. Her mother, Dorothy, is an English teacher. She immigrated to Israel from Belgium when she was 20. She is the youngest child in her family. Her father was in an anti-aircraft unit in the Israeli Defense Forces, and her brother is a pilot. Kertesz spent her childhood growing up in Yemin Moshe in Jerusalem, Israel. She moved to Tel Aviv when she was 14 years old. Kertesz originally was an avid dancer, studying dance from age three and attending the Rubin Academy of Music and Dance. But her last summer living in Jerusalem, before she was to enter ninth grade, while visiting her brother in Tel Aviv she met a casting director in the stairwell of his building, and the casting director offered her an audition for a new television series. She was given the part, and her first appearance was in the Israeli television series Reds, created by brothers Uri Barbash and Benny Barbash, at the age of 14. She was the main character Noa Sperling, a 15-year-old soccer player who creates a girls-only team after being asked to leave the boys' team. The show aired for two seasons. She then had small roles in two series in 2007, Screenz and Custody, created by Irit Linur, in which she played Tamar, the young daughter of a twice-divorced father. Kertesz then acted in the drama series "Masks" on the Yes satellite network. Kertesz came to greater prominence playing in 13 episodes of the 2008 Israeli Channel 10 series as missing 17-year-old Hagar Ben David. That year she also played Avia, an innocent girl, in Israel Channel 10’s Loving Anna. Kertesz played "Segen", a junior officer in the Israeli Defense Forces assigned to protect Brad Pitt's character's life, in the 2013 film World War Z. She auditioned for the part in Tel Aviv, and then in Malta with director Marc Forster and the producers. She also played Onie in the psychological thriller AfterDeath, released in 2015, and is slated to appear in World War Z 2, but that project was ultimately cancelled in 2019.
