The Episcopal Church's House of Deputies, made up of 832 priests and lay people, overwhelmingly approved the agreement Saturday, one day after it won approval from the other chamber of the church's legislature, the House of Bishops.
Leaders of the 5.2 million-member Evangelical Lutheran Church in America approved the alliance last year.
"It enables our two churches to work together in a shared mission to our broken and hurting world," said the Very Rev. Donald Brown, co-chairman of ecumenical relations for the 2.4 million-member Episcopal Church.
"Both our communions will be living into reality Jesus' prayer that all his followers might be one," Brown said.
While they differ in style, the Episcopalian and Lutheran churches in the United States share similar patterns of worship and of regional organization.
Allowing the sharing of clergy will help congregations in areas where one church is strong while the other has a thinner presence. In New England, for example, there is a single Lutheran synod and one Lutheran bishop, while the Episcopal Church has seven dioceses and a dozen bishops. Across much of the upper Midwest, the opposite is true.
The pact, which takes effect Jan. 1, also includes a compromise involving the Episcopal ordination of bishops, who are installed in a laying-on of hands by three predecessor bishops from a line believed to stretch back to Christ's apostles.
The alliance will allow Lutheran clergy to serve in Episcopal churches without such ordinations. New Lutheran bishops, however, would have to go through an Episcopal ordination to serve in an Episcopal church.
A spokesman for the Evangelical Lutheran Church in America, Frank Imhoff, said there is some opposition to the pact among Lutherans, who for centuries have been wary of authority and church hierarchy.
It may prompt some Lutheran congregations to leave the church, said the Rev. Lowell Almen, secretary of the Evangelical Lutheran Church in America, but he stressed that much of the opposition to the pact comes from a misperception of the alliance as a merger.
"It doesn't mean either church body is losing responsibility for its own internal life or giving up its own history," he said. "Perhaps those histories will be enhanced."
Another major issue facing Episcopal Church leaders during their 10-day national convention, which began Wednesday, is the blessing of same-sex unions. The church legislature is expected to consider it next week.
One proposal being discussed would codify the church's unofficial policy of allowing each diocese to decide whether to ordain homosexuals and bless gay relationships. Another proposal suggests the church develop rites for couples who live in monogamous, committed relationships but do not get married.