The bride wore a custom Carolina Herrera gown as she wed former American football player Johnson at the San Ysidro Ranch on Saturday in front of more than 250 guests, including her sister Ashlee Simpson and her fiance Evan Ross, best friend CaCee Cobb and her actor husband Donald Faison, and pal Jessica Alba and her partner Cash Warren.
The happy couple's two-year-old daughter Maxwell served as a flower girl and one-year-old son Ace was given the role of ring bearer. Ashlee's five-year-old boy with ex-husband Pete Wentz, Bronx, also took part in the ceremony.
A statement issued by the newlyweds to People.com read: "We are overwhelmed with complete happiness and love having made our eternal commitment.
"To say 'I do' in front of family, friends and, most importantly, our children has been the happiest moment of our lives."
The nuptials took place a day after Simpson and Johnson hosted a pre-wedding barbecue at the same venue to celebrate America's Independence Day with all of their guests.
The couple began dating in early 2010 and became engaged on the blonde beauty's 30th birthday in November of that year, but the pair had to postpone plans to wed twice after the 33-year-old fell pregnant with their kids.
Simpson was previously married to singer Nick Lachey from 2002 to 2006.