The German model, 45, has been dating musician Tom Kaulitz, 29, for nearly a year and confirmed their engagement on Christmas Eve.
Klum, who is also a judge on America's Got Talent, shared the news with a post on Instagram.
In a black-and-white picture of the pair together, Klum showed off her diamond ring and wrote: "I SAID YES."
Klum, who has three children from her marriage with singer Seal, went public with her relationship with Tokio Hotel musician Kaulitz in May.
They made their first public appearance together as a couple at the Cannes amfAR Gala.
Klum is one of the world's most successful models and became the first German model to be a Victoria's Secret angel. She has also appeared on Germany's Next Top Model and Project Runway.
She married British singer-songwriter Seal in May 2005 with a beach ceremony in Mexico.
The couple share three children. They announced their separation in January 2012 and their divorced was finalised in October 2014.