The 42-year-old actress and 35-year-old musician will marry Monday, Jan. 5, at their home in Beverly Hills. The pair are said to have held a rehearsal dinner over the weekend, and party rental trucks, flowers and wedding planner Yifat Oren were spotted at the couple's house Monday morning.
"There is a lot of security and they are trying to keep the wedding hush-hush by telling neighbors that Cameron is having a pre-Golden Globes party tonight," an insider told People. "It will start past dark tonight. They are setting things up in the lush backyard."
Diaz and Madden were introduced by the musician's sister-in-law, Nicole Richie, and started dating in May 2014. News of their engagement broke December 19, and sources told Us Weekly, "Everyone thinks it's wild, but are so happy for them."
Diaz previously dated Justin Timberlake and Alex Rodriguez, while Madden was linked to Sophie Monk and Paris Hilton. The actress is rumored to reprise Elizabeth Halsey in Bad Teacher 2, and Madden last released The Madden Brothers album Greetings from California in September 2014.