"Today is the day. There are no more tomorrows. And I could NOT be happier!" he Tweeted about the ceremony held at Camp Lucy, Dripping Springs, Texas, before 140 friends and family members.
The groom's father, Butch, was best man, and the bride's sister, Lindsey, was maid of honor – while the couple's dog, Truffle, served as flower girl. The bride and groom wrote their own vows.
"Two families became one today," added Porter, 33, along with an Instagram pic.
On the NBC football drama, the Nebraska-born and bred Porter played injured high-school football star Jason Street, and he met Mayfield, a cheerleader at the University of Texas at Austin, on the set of the show in 2008.
He now plays attorney George Tucker on The CW's Hart of Dixie.