Ono, known for her life long dedication to peace and environmentalism, tweeted a controversial image on late Wednesday (Australian time) showing John Lennon's glasses covered in blood, a hazy image of New York's Central Park in the background.
The image was accompanied by the text:
"Over 1,057,000 people have been killed by guns in the U.S.A. since John Lennon was shot and killed on December 8, 1980."
Ono tweeted: "31,537 people are killed by guns in the USA every year. We are turning this beautiful country into war zone.
"Together, let's bring back America, the green land of peace.
"The death of a loved one is a hollowing experience. After 33 years our son Sean and I still miss him. Yoko Ono Lennon"
Ono was herself the victim of gun violence when her husband, Lennon, was shot and killed outside their Dakota building in New York City on December 8, 1980. The glasses were worn by Lennon himself at the time of the shooting and are stained with his blood from the attack.
Ono also tweeted a quote from an interview the pair gave shortly after their wedding. "20 March 1969: We want to talk to the young people all over the world, because we want to say we are with them."