The signing ceremony occurred at Washington Place mansion and museum in Honolulu.
Civil unions will begin on January 1, 2012.
Hawaii is the seventh state to approve of civil unions or a similar legal recognition for gay couples. Five states plus the District of Columbia currently allow same-sex marriage.
GLAAD hopes that the Hawaiian media will focus on the positive effects civil unions will have on not just the gay and lesbian community, but on all of the citizens of Hawaii.