The host announced her departure on Thursday's program, with her last day being September 15. Her replacement will be announced on Friday.
Trioli came to the job in October 2019, switching from New Breakfast TV co-host, to replace Jon Faine who had spent 23 years in the mornings role.
"After a difficult period of dealing with multiple illnesses in my family and also with the realisation that I think you're lucky if you get even one warning about how long you have on this earth with the people that you love, I now find myself at that stage of life that requires me to live and to work in a different way," she announced on ABC Radio on Thursday.
"After almost 20 years of working to the hardest alarms at the ABC has to offer...it's a change that feels unavoidable for me right now."
She will present a prime time television arts show in 2024.
"It is very hard to leave," she said.
"This is and has always been one of the most important chairs in journalism and broadcasting in the country."
ABC New Breakfast presenter Michael Rowland said it was a sad day for many listeners.
"As a fellow early morning warrior (and former work husband) I can completely, and jealously, understand the switch to normal hours! Go well," he posted to social media.
Trioli previously worked for The Age newspaper in Melbourne and presented the morning program on ABC Radio Sydney before becoming a founding anchor of the broadcaster's breakfast television program.
ABC managing director David Anderson joined Trioli for the announcement and congratulated her for having a lasting impact on her audience.
"People choose to spend time with you, they love the idea that you're there for them," he said.
"What you do, the way you interview people, hold people account, as people share their lives with you."
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