Jessica Reynolds grew up in Seahill, between Holywood and Bangor in County Down. Her parents worked as teachers at Rockport School. The family lived in a staff house on the school grounds from when she was five years old.

Reynolds parents raised her in a non-denominational household. Her mother came from a working-class Catholic family in Exeter, England. Her father held a culturally Protestant background. At age seven, a child in Bangor asked Reynolds if she was Protestant or Catholic. She did not know the answer.

Her family focused on sports. Her father Josh was a champion hurdler. Her brother Ben competed for Ireland and Northern Ireland in the 110-metre hurdles. Reynolds trained in gymnastics four or five times a week from age seven to ten.

Reynolds decided to pursue acting after watching the film Thirteen at age twelve or thirteen. She studied at Liverpool Institute for Performing Arts in 2016. There, her Irish accent made her feel she would not work professionally.

Reynolds appeared in the Kneecap film. The experience led her to embrace an Irish identity after previously identifying as British. She now finds calling herself Irish most fitting.

Reynolds currently films Close to Home in Belfast. The project adapts Michael Magee's novel for Channel 4 and stars Anthony Boyle.

Reynolds leads the cast as Emma Harte in A Woman of Substance on Channel 4. Filming took place in Yorkshire.