The couple of seven months got married in an "intimate ceremony" at the couple's Los Angeles home Monday night, their rep told People.
"We couldn't be happier to begin our new journey together surrounded by our closest family and friends," the couple said.
More than 90 guests, including Reese Witherspoon and Gwyneth Paltrow, attended the 7:30 p.m. ceremony, sources told People. Revelers partied the night away in a backyard tent reception.
The atmosphere was set by candles, dim-lighting and mostly white flowers, thanks to the handiwork of celebrity wedding planner Yifat Oren.
Party planners had to "keep the wedding hush-hush" and tell neighbors the security was for a pre-Golden Globes party, a source said.
"It was a big wedding, but they still managed to make it feel very personable," a source told people. "Only their families and very special friends attended. It felt very down-to-earth and sweet."
Good Charlotte rocker Madden, 35, popped the question to the 42-year-old "There's Something About Mary" star less than a month ago.
The couple exchanged vows a day after Diaz got down with friends at her bachelorette party in a Los Angeles hotel, People reported. The pair enjoyed a rehearsal dinner in Beverly Hills with loved ones over the weekend,
They were first introduced by the rocker's sister-in-law, Nicole Richie, who is married to his twin, Joel.
"I'm going to take responsibility for everything!" Richie said on "Watch What Happens Live!" after news surfaced of the pair dating. "I approve of anything that's going to make Benji happy."
It will be the first marriage for both and neither have any children.
Prior to her whirwind romance with the Madden, Diaz previously dated Justin Timberlake, Alex Rodriguez and Sean (Diddy) Combs.
Madden's list of exes includes Paris Hilton and he reportedly dated Holly Madison.
