Herbert told the crowd that everyone should have "the courage and vision to do what's right.
"To have successful communities, we need successful families," he said.
Alan and Suzanne Osmond emceed the event, dubbed the Celebration of Marriage, held on the same day the U.S. Supreme Court heard oral arguments in the Proposition 8 case. California's ballot-approved initiative defined marriage as between a man and a woman.
The Rev. Greg Johnson, of Standing Together, a group of evangelical churches, reiterated the one-man-one-woman message.
"There's a lot of love in this room, as well as opinions," Johnson told the crowd. "God loves every person in this room."
But Johnson said he supports "natural" marriage, which he said he gets from the Bible.
The event, as well as the one Monday by gay-rights advocates, mirrored rallies around the country, as the high court hears arguments on Proposition 8. On Wednesday, the case of Defense of Marriage Act (DOMA) will be heard.
The event at the Capitol was equal parts speeches and music acts, including the Osmond grandchildren and a bluegrass group called The Dansie Family Band.
Several in attendance praised the governor's and pastor's remarks, seeming to not want to offend those holding other views.
"It's not that I'm against gay people," said Mary Dobson, of Sandy, who came with her husband and two children. "This is the way my faith tells me how to live a righteous life."
On a table in the back of the room, people were encouraged to sign a certificate of marriage, which stated in part: Marriage is the union of a man and woman whose marital privileges are based upon their commitment to protect and nurture the children that may be created as a result of their union.
People on the balcony held rainbow-colored flags and signs that read, "God is love," and "My family values respect families."
Evangelical church members Stan and Mary Miller said they were not offended by the protests, but they said they wanted to show their support for traditional marriage.
Stan Miller read from a pamphlet being passed around entitled "Why Marriage Matters," quoting several Bible passages: "And the Lord God said, It is not good that the man should be alone, I will make him a help mate (Genesis 2:18)."
"If you believe in the Bible, then it's spelled out," he said. "This is what we believe, perhaps others don't, but I've got to stand up for what I believe in also."
Several participants said Utahns have already dealt with the gay-marriage issue. In 2004, Utah voters overwhelmingly approved a constitutional amendment banning gay marriage. It specifically does not recognize same-sex marriages, even if they are performed in a state where they are legal.
"Maybe they can get married in other states," Mike Johnson said, referring to gay marriage allowed in nine other states. "But that's not something I think a majority of Utahns would want here."
Nick Enwall, who returned to Utah after being an attorney in Illinois, said everyone now looks to the Supreme Court, which is expected to rule on the two gay-marriage cases in June.
Enwall said the issue should be left up to each of the 50 states.
"I think we're unique in Utah with our history," Enwall said. "And I applaud the governor for being here and standing up for what's right."