The 41-year-old actor, who played Richard 'Stabone' Boner in the 1980s sitcom, was discovered dead in a Vancouver park last month.
Speaking to E! Online, a representative for his father Walter said: "It was a celebration of life.
"All of the family was there and a lot of his actor friends and filmmakers flew down and joined in. It was not all happiness, I must say. There was a lot of sadness, but there were some very nice high points."
The spokesperson continued to say that Koenig's sister and brother-in-law gave eulogies at the memorial - which took place at the Inn Of The Seventh Ray in Topanga Canyon - while his parents chose not to speak.
"It was tough for them," he explained. "But there was some closure, and I think that was important."
Mourners, who included Star Trek and Growing Pains castmembers, were reportedly also shown a ten-minute movie depicting Koenig's life.