The Bavarian star has lavished praise on the 66-year-old for taking him under his wing early on in his career, while he shared his ambitions of becoming a key player for Germany
The veteran trainer first worked with the 23-year-old at Bayer Leverkusen five years ago, as the Germany international spent 18 months on loan in North Rhine-Westphalia, before they were reunited at the Allianz Arena in 2011.
Kroos initially struggled to establish himself in Bavaria upon returning from the BayArena, but he believes being subjected to Heynckes' presence at a young age was pivotal to his development.
"Heynckes was the coach who gave me the chance to play in the Bundesliga. That's why I'll be sad when he retires," he told reporters.
"I'll always be grateful. Without him I wouldn't be the person that I am today. That's his work.
"I'm very comfortable with my development. But that doesn't mean I'll do less in future. There's the next step which I can and must reach."
Mannschaft and Borussia Monchengladbach legend Gunter Netzer recently claimed Kroos has the potential to become a world-class talent in the next few years, but the playmaker is more concerned about becoming a regular starter for his country.
"Without a doubt, Netzer understands football," he added. "Maybe he sees my potential if he says something like that.
"I play for Bayern who are the best team after Barcelona. And when you're a starter there, you're on the right tracks. But I wouldn't judge myself in public. That would be embarrassing.
"Sure, I want to be a starter for Germany, too. The European Championship was dissatisfying for me [as I played only 108 minutes]."