The victims hailed from more than 30 countries.
"As friends and family gather in Ethiopia from all over the world to honor the memories of their loved ones, I pay tribute to the victims of this accident and wish their families continued strength," Ethiopian Prime Minister Abiy Ahmed said Tuesday on Twitter.
Security forces blocked journalists from attending the ceremony at the site, though vehicles transporting families could be seen heading there.
Some families have made multiple trips to the site in the past year, including in the immediate aftermath of the crash and when victims' remains were sent to their home countries towards the end of 2019.
But for Frenchwoman Catherine Berthet, who lost her 28-year-old daughter Camille, this week marked the first time she had set foot in Ethiopia since the disaster.
She decided to attend the ceremony at the urging of her therapist in hopes it would provide some form of closure, she told AFP.
"If you lose your child in a car accident, you can often see the body, and that's important. I won't have this chance because my daughter died in a plane crash - her body was turned into a million pieces," Berthet said.
"So it's important to go to the country where she passed her final moments."
Virginie Fricaudet, president of an association of French victims' families, said she expected Tuesday's ceremony would help "close a chapter", though she acknowledged that relatives of the dead were still grieving.
"For me this commemoration is about bringing together this immense family that is connected by the tragedy," said Fricaudet, whose brother died on Flight 302.
On Monday, the families of Flight 302's nine French victims attended a memorial service at the French embassy in Addis Ababa, setting white roses at the base of nine jacaranda trees planted on the embassy grounds a year ago.
It was unclear what exactly Ethiopian Airlines had planned for the ceremony on Tuesday.
As recently as January, the company hoped to use the anniversary to announce the winner of an architectural design competition for a memorial, though the plan drew pushback from some victims' families who objected to what they perceived as a rushed timeline.