Onana has not yet officially signed for Inter, though he did say his goodbyes to Ajax while long-serving Handanovic is due to pen a contract extension soon.
And Gazzetta dello Sport report both will play a key role next season with no nominated first-choice goalkeeper.
Handanovic has been at Inter since 2012 and has been one of the best goalkeepers in Serie A during that time. He won his first trophy at the club with the 2020-21 Scudetto and has since added the Supercoppa and Coppa Italia.
Onana has been at Ajax since graduating from the academy and has won three successive Eredivisie titles as well as the Dutch Cup on two occasions. He was also a key part of the side which reached the 2018-19 Champions League semi-finals.