"We exchanged emails with Jack (Dorsey)", the boss of the social network, told the British prince during an online conference organized by Wired, an American magazine specializing in technologies.
"I warned him that his platform was letting (users) stage a coup," he continued.
"This email was sent the day before and I haven't heard back from it since."
At the end of 2020, the false rumor of rigged elections, hammered out by former US President Donald Trump, fueled the anger of many conservatives and conspirators.
Hundreds invaded Congress during the certification of Joe Biden's victory on January 6.
Five people were killed during or shortly after the attack.
In the process, Facebook, Twitter and other major platforms have banned Donald Trump and the extremist movements involved in the riots.
All, aware of the risks, had already taken measures to try to curb disinformation and recruitment by far-right organizations.
They were deemed largely insufficient by many elected officials and NGOs.
Twitter declined to comment on Prince Harry's comments.
"The internet is becoming a den of hatred, division and lies. This is not normal. Especially for anyone with children," he continued during a discussion of the disinformation.
"As humans, as individuals with the capacity to make choices and take decisions, they might worry a little more about the safety of people," he said.
Prince Harry, sixth in order of succession to the throne, and his wife Meghan Markle stepped back from the British monarchy in 2020.
They moved to Los Angeles and signed lucrative deals, including with Netflix and Apple TV +.
Harry also accepted a management position with a San Francisco-based coaching company.
In March 2021, they rocked the crown in an interview on American television, which bombarded the United Kingdom.
Sometimes moved to tears, Meghan Markle said in particular that she was tormented by suicidal thoughts and raised questions within the royal family on the color of the skin of their son Archie during his pregnancy.
© 2021 AFP