Lennon was murdered outside his Manhattan apartment building 30 years ago.
Fans flocked to Strawberry Fields, the Central Park garden dedicated in his honor, in Central Park on the anniversary to pay tribute to Lennon.
Many also spent the day at his star on the Hollywood Walk of Fame.
"Today is not so much a day of mourning, but more a day to celebrate John's life, music and creative spirit," said organizer Jerry Rubin.
Meantime, Rolling Stone magazine is releasing Lennon's final interview on the 30th anniversary of his death.
In the interview, he complained about his critics, saying they were just interested in "dead heroes."
Lennon also talked optimistically about his family and future. The magazine also included an essay by Yoko Ono recalling her final days with her husband. The issue using the full interview will be on magazine stands on Friday.
In Lennon's hometown of Liverpool, a vigil was held around the Peace and Harmony sculpture, recently unveiled by Lennon's former wife, Cynthia, and their son Julian in Chavasse Park.
His widow, Yoko Ono, asks fans to join her in remembering Lennon with love and respect.
The Associated Press contributed to this report.