By a 104-30 vote, bishops at the Episcopal General Convention moved to "collect and develop theological resources and liturgies" for blessing same-gender relationships.
The new prayer could be ready for approval at the next convention in three years.
The resolution acknowledged the growing number of states that allow gay marriage, civil unions and domestic partnerships.
"We certainly feel a deep need to be able to proclaim the love of God in the midst of a changing reality," Suffragan Bishop James Curry of the Diocese of Connecticut told the Associated Press. Connecticut is one of six states that are legalizing same-gender marriage.
A day earlier Episcopal leaders declared gays and lesbians eligible for any ordained ministry in the church.
The Episcopal Church is the U.S. branch of the "World Anglican Communion." Six years ago the Episcopalians caused an uproar by consecrating an openly gay bishop.
Many believe the global fellowship is on the verge of breaking apart over the gay-lesbian issue.
The Associated Press contributed to this report.