The company supremo told Recode that Twitter needs to do more in order to combat abuse, conceding that putting the burden on victims to report abuse was not the way forward.
Asked what grade he would give himself for "tech responsibility", Dorsey said: "Myself? C. We've made progress but it has been scattered and not felt enough. And we've put most of the burden on the victims of abuse (that's a huge fail)."
Dorsey has also hailed Tesla boss Elon Musk's tweeting, saying he finds the controversial tech businessman to be an exciting and influential figure on the platform.
He explained: "I like how @elonmusk uses Twitter. He's focused on solving existential problems and sharing his thinking openly. I respect that a lot and all the ups and downs that come with it."
Musk was pleased to learn of Dorsey's remarks.
He wrote on the micro-blogging site: "Thanks Jack. Twitter rocks. (sic)"
Despite this, Twitter has come under fire over recent years for its handling of various issues, including fake news and bullying.