"Tonight while we watch @carolsdomain I will be taking a moment to celebrate and reflect on the wiggly wonder that is @emma_wiggle," he said on Thursday.
"We met in 2009 and have made a lifetime of memories in what has been a jam packed 12 years of friendship and fun."
He went on to add: "When I look over to Emma I am overcome with a wave of emotional happiness. For so many children and families all over the world, the girl with the bow in her hair will live on forever in their hearts including mine."
Lachy also shared a poem dedicated to Emma, which read: "For all of our shows. For all of our songs. For all the years. The yellow bow belongs.
"To the girl named Emma. For everything you’ve done. The dances, the sign language. And the way that you sung.
"For all that comes next. You’ll thrive in all that you do. Emma Wiggle from Lobby and Lachy. A love felt thank you."
Emma and Lachy are still close friends after announcing their split in 2018 after two years of marriage, and have since publicly moved on with other people.
Lachy is engaged to ballet dancer Dana Stephensen, with whom he shares one-year-old twin girls Lulu and Lottie.
Emma is also engaged to Oliver Brian, who works with The Wiggles as a musician.