The Annie star began dating the musician in May after Nicole Richie set them up (Richie is married to Madden's twin brother Joel). "I approve of anything that's going to make Benj happy," Richie told Watch What Happens Live host Andy Cohen in July.
This is the first engagement for Madden, 35, and the second for Diaz, 42. She was briefly engaged to Jared Leto in 2000 and previously dated Alex Rodriguez, Justin Timberlake, Matt Dillon, Diddy and Edward Norton.
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