The move comes just weeks after North Carolina voters approved an amendment to the state constitution that defines marriage as only between one man and one woman and makes it the only domestic union the state recognizes.
North Carolina NAACP President Rev. Dr. William J. Barber, II told reporters gay marriage is a matter of civil rights, and the nation's most prominent civil rights organization will support it.
"The NAACP does not have or hold a position on same-sex marriage from a personal, religious or moral perspective. We did not endorse bi-racial marriage in the 1960s. We don't endorse heterosexual marriage or people living together outside of marriage and we don't endorse same-sex marriage. What we do endorse is a stance against any attempt to codify discrimination or hate in the law," said Barber.
Barber's words echoed national leaders who said the NAACP's position on the issue is consistent with the equal protection provision of the U.S. Constitution.
"The mission of the NAACP has always been to ensure political, social and economic equality of all people," Board Chairwoman Roslyn M. Brock said in a statement. "We have and will oppose efforts to codify discrimination into law."
"Civil marriage is a civil right and a matter of civil law. The NAACP's support for marriage equality is deeply rooted in the Fourteenth Amendment of the United States Constitution and equal protection of all people" said NAACP President Benjamin Todd Jealous, a strong backer of gay rights.
Same-sex marriage is legal in six states and the District of Columbia, but 31 states have passed amendments to ban it.
Gay marriage has divided the black community, with many religious leaders opposing it. In California, exit polls showed about 70 percent of blacks opposed same-sex marriage in 2008. In Maryland, black religious leaders helped derail a gay marriage bill last year. But state lawmakers passed a gay marriage bill this year.
Pew Research Center polls have found that African Americans have become more supportive of same-sex marriage in recent years, but remain less supportive than other groups. A poll conducted in April showed 39 percent of African-Americans favor gay marriage, compared with 47 percent of whites. The poll showed 49 percent of blacks and 43 percent of whites are opposed.