A small group of the actor's close friends and family gathered at Westwood Village Memorial Park for the 30-minute service.
Actress Naomi Watts, who dated him for two years from 2002, was among the guests, along with his ex-fiancée Michelle Williams and two-year-old daughter Matilda.
Reports claim that there was a high security presence at the memorial following a religious group's vow to picket it in protest at Ledger's role as a gay cowboy in Brokeback Mountain.
The group moved on to a private dinner at the Beverly Hills Hotel after the service.
An onlooker told Us Weekly: "Even though it was a sad occasion, everyone was smiling, hugging each other and holding hands. It was a really positive group."
The 28-year-old was found dead at his New York apartment last Tuesday.
He will be buried later this week in his hometown of Perth, Australia.
> Obituary: Heath Ledger