Iling-Junior contributed an assist in three UEFA Youth League appearances for Chelsea last term and is known for his speed on the wing.
"Full of vast emotions," the England under-17 international wrote on Instagram. "Being at Chelsea from such a young age has truly built me.
"Not only as a the player I am today but also as a person. It's been a blessed journey and I'm deeply thankful for all those in the academy.
"From the groundsmen, education, kitchen, staff, players, coaches, the list goes on. I'm filled with gratitude at the time and effort put into my development, leading me to where I am today.
"I would also like to give thanks to the people around me, my family and friends who have consistently supported me.
"Finally, I'd like to thank God for blessing me with this opportunity and protecting me throughout. This is just the start, I wish Chelsea all the best for the seasons ahead."
He followed that up with a picture of himself putting pen-to-paper on a contract with the Bianconeri alongside the caption: "Pleased to announce my signing to Juventus ,can't wait to get started. To new beginnings Forza Juve."
Alongside Iling-Junior, Juve also presented 19-year-old Felix Nzouango Bikien, who they signed from Amiens.