Lopez married singer Marc Anthony in a secret wedding on June 5, 2004, less than a week after his divorce was finalized from former Miss Universe Dayanara Torres. The guests were invited to an "afternoon party" without knowing that they were going to a wedding. Years before they married (or even became a couple), she and Marc Anthony sang a song together called "No Me Ames" which appeared on her album On The 6. Almost immediately, rumors began that the ceremony was a "shotgun" and that Lopez was pregnant. Lopez had said in the past that, as a practicing Catholic, she would never have a baby without being married. Complicating the situation is Anthony's refusal to confirm his marriage to Lopez and the fact that his divorce took place in the Dominican Republic less than a week before his reported marriage to Lopez, making it potentially invalid in the United States. The couple has since confirmed their marriage, although Lopez refuses to discuss it. Lopez has become a stepmother to the two sons, Cristian and Ryan, that Anthony had with Torres and also to his daughter, Arianna, from a previous relationship.

Lopez announced her engagement to Ben Affleck in October 2002, after Affleck gave her a ring worth a reported $3.5 million. The marriage, planned for September 14, 2003 in Santa Barbara, California, was called off a few days before the event. She and Affleck split for good in January 2004. Their relationship was parodied on the South Park episode, "Fat Butt and Pancake Head" that aired on April 16, 2003.

Her second marriage was to Chris Judd, her former backup dancer. She met Judd while filming the music video for her single "Love Don't Cost A Thing". The two were married on September 29, 2001 at a home in a Los Angeles suburb officiated by attorney Barry Hirsch. The marriage ended in June 2002.

From 1999 to 2001, she dated rapper and producer Sean "Diddy" Combs. Both were arrested in connection with a nightclub shooting in December 1999. Police found them with a stolen gun. The charges against Lopez were dropped. Combs was indicted but was eventually tried and acquitted. Their breakup was announced on Valentine's Day, 2001.

Her first marriage, to waiter Ojani Noa, occurred on February 22, 1997. He was later named the manager of Lopez's restaurant, Madre's. They divorced in January 1998. On April 10, 2006, Lopez sued Noa,claiming he breached a confidentiality agreement he signed by shopping around a tell-all book about their relationship.