Shirvington confirmed on Monday he will take Koch's coveted spot on the couch alongside Natalie Barr after days of speculation.
"It was the worst kept secret," he said live on air.
"(I have) mixed emotions, just amazing, daunted, so excited, happy, cannot tell you the honour and privilege this is Kochie particularly, a huge job and an exciting job."
The former sprinter and father-of-three has been a regular fill-in for Koch on Fridays, which he said served as good training for his new role.
However, he was still nervous about the permanent gig.
"I think I'm more nervous than I have ever been, including the Olympics," he said.
Koch said Shirvington was the "perfect fit" for the job.
"You've been fantastic filling in every Friday, it's been sensational," Koch said.
"You are going to be sensational, you are going to be the perfect fit."
Seven Director of Morning Television Sarah Stinson his appointment marked the start of an exciting new chapter for Sunrise.
"Dedicated, talented, warm and dependable, he is more than ready to permanently join Nat and the team each morning as Australians start their day," she said in a statement.
Shirvington will co-host his first edition of Sunrise with Barr next Monday, June 12.
Koch recently announced his departure after 21 years on the show.
After initially filling in for a sick colleague, Koch landed in the host chair in 2002 at a time of rapid experimentation in the makeup of Seven's morning TV.
Koch has co-hosted more than 5300 shows over the years alongside Melissa Doyle, Samantha Armytage and most recently Barr.
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