Born on July 24, 1969 in the Bronx, a borough of New York City, Jennifer Lynn López grew up in the Bronx's Castle Hill neighbourhood. David López and Guadalupe Rodríguez, her parents, met in New York City after being born in Puerto Rico. David was employed by Guardian Insurance Company as a computer technician following his military service. For the first ten years of López's life, Guadalupe was a stay-at-home mum. She then went on to work as a Tupperware salesperson and a kindergarten and gym instructor. Following 33 years of marriage, they got divorced in the 1990s.
Lopez is the middle child; her sisters are Lynda, who is younger, and Leslie, who is older. The bedroom was shared by the three. Lopez has characterised her family as "strict". She grew up in a Roman Catholic home, going to Sunday Mass and receiving her education at Holy Family School and Preston High School, which was exclusively for ladies. In addition to playing softball and gymnastics, López competed at the national level in track. She participated in school productions as a dancer and led a Godspell production.
López and her sisters were encouraged to sing, dance, and write plays for family gatherings because there was "lots of music" in their traditional Puerto Rican home. The young López was particularly influenced by West Side Story, and she always wanted to be a performer. She studied ballet, jazz, and flamenco at the Kips Bay Boys & Girls Club as a youngster. She also taught dance to younger children, among them Kerry Washington. She worked as a part-time secretary at a law company after high school and attended Baruch College in New York for one semester to study business.
In 1989, López travelled throughout Europe for five months as part of the musical revue performance Golden Musicals of Broadway, which was her first paid employment. Being the only chorus member without a solo, she later described the experience as a turning point in her life when she understood the value of having a "tough skin" in the entertainment industry. She performed dancing moves with MC Hammer in a Yo! MTV Raps programme in 1990, and she spent four months touring Japan as a chorus member for Synchronicity. She was employed as a backup dancer for New Kids on the Block's "Games" performance at the 1991 American Music Awards after she returned to the United States.
Additionally, she toured the United States with local productions of Oklahoma and Jesus Christ Superstar. Lopez further performed in music videos at this time for songs like "Summertime" by Doug E. Fresh, "Can't Stop Loving You" by Richard Rogers, "Rampage" by EPMD, and "(Hurt Me! Hurt Me!) But the Pants Stay On" by Samantha Fox.