Ons Jabeur was born to Samira and Ridha Jabeur in Ksar Hellal, a small town in Tunisia. She grew up in the larger nearby coastal town of Sousse. Jabeur has two older brothers, Hatem and Marwen, and an older sister, Yasmine. Her mother played tennis recreationally and introduced her to the sport at the age of three. Jabeur trained under coach Nabil Mlika for ten years from ages four to thirteen, originally starting to work with him at a tennis promotion centre at her school. When she was ten years old, her club did not have their own tennis courts and she could only train on courts at nearby hotels. At twelve years old, Jabeur moved to the capital city of Tunis to train at the Lycée Sportif El Menzah, a national sport high school for the country's up-and-coming athletes, where she stayed for several years.

She also later trained in Belgium and France starting at the age of 16. Jabeur credits her parents for the sacrifices they made when she was growing up, saying, "My parents sacrificed a lot of things – my mom used to drive me everywhere around Tunisia to go play the tournaments, and she encouraged me to go to a special school to study. That was a big sacrifice to see her little girl going for a dream that, honestly, wasn't 100% guaranteed. She believed in me and gave me the confidence to be there."
What sacrifices did Ons's parents make to help her tennis career?
Ons's mother used to drive Ons all around Tunisia to play tennis tournaments and encouraged Ons to go to a special school to study.