The couple — who first said "I Do" in front of hundreds of guests in Malibu on Jan. 10, 2009 — wed again with just the two of them and a minister outside Santa Barbara, Calif.
"It was a total surprise for Fergie," a source tells Us.
Duhamel, 37, whisked Fergie, 34, away via private helicopter from Los Angeles to the resort town (where Oprah has a home), according to RadarOnline.com, which first reported the news.
There, a limo was waiting to bring the couple — who first began dating in 2004 — to the luxe Bacara Resort & Spa, located about 20 minutes away.
During their 15-minute ceremony, held on a bluff overlooking the ocean, Fergie was "crying and very emotional," a source tells Radar.
Another insider describes the moment to Us as "really romantic, great views of the Pacific, sunset ceremony."
Afterward, the couple had a romantic dinner at the resort's upscale Miro eatery.
"They had the whole restaurant to themselves and left before the first customers came in," a source tells Radar.
Following the meal, the couple left hand-in-hand to return to the helicopter and fly back to Los Angeles.
Fergie and Duhamel's first year of marriage has been rocky.
In November, a stripper named Nicole Forrester alleged they carried on an affair while he was shooting the comedy Life As We Know It in Atlanta, a claim both Fergie and Duhamel have denied.
A source tells the new issue of Us Weekly that enduring the ordeal actually made their marriage stronger.
For access to all our exclusive celebrity videos and interviews – Subscribe on YouTube!