Fisher, 60, died of a heart attack Dec. 27 and Reynolds, 84, died a day later.
Todd Fisher, the surviving brother and son, told gatherers the service should reflect the Hollywood glamour Reynolds and Fisher embodied.
"The entire thing I'm calling a show, not a memorial ... because my mother loved shows," he said. "This show was designed for you to be in our living room together ... celebrating two amazing women."
The crowd was eclectic, some clad in elegant dresses and suits, others in costume as Princess Leia, Fisher's iconic character in the Star Wars movies.
The Los Angeles Times reported the Hollywood Hills Hall of Liberty at the Forest Lawn cemetery was packed to capacity, with 1,200 attendees inside and hundreds more outside.
Video tributes to the women's careers were shown as well as famous scenes from their most famous movies -- Star Wars for Fisher and Singin' In the Rain for Reynolds.
Comedian Dan Aykroyd, who was briefly engaged to Fisher in the 1970s, lamented her passing.
"We shouldn't be here so soon in our lives," he said.
A private funeral for family and close friends was held in January.