Takei, 71, and Altman, 54, were married Sunday in a multicultural ceremony at the Japanese American National Museum that featured a Buddhist priest, Native American wedding bands, a Japanese Koto harp and a bagpipe procession.
The couple, both clad in white dinner jackets with black pants, made a grand entrance to the tune of "One Singular Sensation" from the Broadway musical "A Chorus Line." They stepped into a circle of yellow roses and lilies, where they shared a traditional Japanese tea ceremony and were wed by a Buddhist priest.
The couple, who have been together for 21 years, wrote their own vows.
Altman said that he had called Takei many things during their two decades together - "life partner, significant other" - but that their marriage represented "a dream come true for me."
"I can add 'my husband' to the list of things I call you," he said.
Takei called his longtime partner an "organized, detail-obsessed, punctuality-driven control freak."
"I'm easygoing with details, so we're a good fit," he said in the trademark baritone recognizable to all "Star Trek" and Howard Stern fans.
"I vow to care for you as you've cared for me ... and to love you as my husband and the only man in my life," Takei said as he held Altman's hands.
The priest then pronounced them "spouses for life." A bagpiper played as the newlyweds walked out, followed by friends, family and a few members of the press.
Takei said he and Altman chose to make their wedding public - and have been outspoken gay-rights advocates for years - for the sake of democracy.
"We have a relationship that's been stronger and longer-lived than some of our straight friends, and yet we were not equal," Takei told The Associated Press before the ceremony. "What this does is give us that dignity; (it's) being part of the American system and being whole. We're making the American system whole as well, as America is becoming more equal."
Such activism is nothing new for Takei. He participated in the civil rights movement, served as a Democratic delegate in 1972 and fought for redress for those - like his own family - who were forced into internment camps after World War II.
"I grew up determined not to be marginalized," he said. "That served as an incentive for me to be proactive."
He and Altman were among the first couples to receive a marriage license in West Hollywood when the state began granting licenses to gay couples on June 17.
"A quarter century ago, when I first met Brad, (marriage) was the farthest thing from our imagination," Takei said. "But what seemed impossible at one time becomes, over the passage of time, more and more 'what if' and 'why not.' We have to participate in moving society along to be a better democracy."
Wedding guests included "Star Trek" stars Walter Koenig and Nichelle Nichols, who served as best man and best lady, Hollywood executives, local and national government officials and the couple's relatives from around the world.
Keeping with the multicultural theme, guests dined on Asian/Baja Californian fusion cuisine and took home Japanese tea-ceremony treats in boxes printed with the phrase: "May sweet equality live long and prosper."
The "Star Trek" star and his manager plan to honeymoon in Argentina and Peru.