Kilmister died in late December, just days after being diagnosed with an aggressive form of cancer, the band said.
His passing was received by an outpouring of grief from musicians and other celebrities, including Ozzy and Sharon Osbourne, Juliette Lewis, Ice T and others.
For his memorial service, the band – which would be disbanding after Lemmy's death – planned something equally large: a global gathering in remembrance and celebration for a "warrior and a legend."
As friends and family gathered in Hollywood's Forest Lawn Memorial Cemetery, the service was simulcast live on the band's YouTube page.
"Wherever you are, PLEASE get together and watch the service with fellow Motörheadbangers and friends. GO to your favorite bar, or your favorite club, make sure they have access to an internet connection and toast along with us," the band said.
They continued, "Whatever your venue, and however you can, let's be sure to gather globally ... and celebrate the life of our dear friend and irreplaceable icon."
Fans were asked not to attend the event but rather to watch it online.
The memorial service was decorated with photographs of the iconic rock band and flowers, including a floral arrangement in the shape of the Ace of Spades, after the band's famous 1980 song.
Friends (like wrestler Triple H), rock stars (including Anthrax's Scott Ian, Guns N' Roses' Slash, and Lemmy's bandmates spoke at the service, which was a mixture of reflection, laughter and, appropriately, lots of NSFW language.
Lemmy's son Paul recalled his father's life as a "stage warrior" and "free spirit" while Alice in Chains' Mike Inez joked about a floral arrangement in the shape of "a giant speed line."
Judas Priest's Rob Halford also talked about the "lots of love" in the room and said "laughter was the overriding emotion" with the band when they were on tour.
The metal singer also told a touching story about holding Lemmy's hand during a break from touring when they were waiting in an airport in South America. "I kissed him and told him I loved him," Halford said.
"Here was a man who lived life and rock 'n' roll on his own terms," Halford said. "A true rock 'n' roll maverick."