The former Westlife singer tied the knot with Irish DJ Williams in a ceremony at the Castello of Vincigliata in Florence, Italy, yesterday (September 2).
32-year-old McFadden and Williams, 26, have been dating since May 2011. They announced their engagement in January.
The main details of the ceremony are unknown but it has been confirmed that McFadden's daughters from his first marriage to Kerry Katona acted as bridesmaids.
The couple had the ceremony in Florence after they initially made their union official at a registry office in Dublin with close friends and family present.
Guests at the ceremony in Italy included McFadden's Australia's Got Talent co-judge Dannii Minogue.
McFadden - who was previously engaged to singer Delta Goodrem - had been tweeting about the special day the week before.
Last week, he wrote: "Look out Italy the Irish and the Aussies are coming in hot!!!!!!!! (sic)"
Yesterday, he tweeted: "I'm getting married today. #justsayin. (sic)"