"My musical brother... My friend... The one who showed me the possibilities within myself, changed everything, and kept his integrity until the end, is gone," he captioned a vintage black-and-white shot of Prince clad in a trench coat.
Kravitz, 51, has long been an admirer of Prince, who died Thursday at his Paisley Park compound in Minnesota at age 57.
The duo helped ring in the new millennium together when they took the stage to perform Kravitz's hit song "American Woman" at Prince's New Year's Eve Rave Un2 the Year 2000, which was broadcast on Pay-Per-View on New Year's Eve 1999.
The collaboration had a clear impact on the "Fly Away" singer. In 2014, Kravitz told the Huffington Post that he dreamed of forming a band one day. When asked who would be part of it, he mentioned only one musician by name: Prince.
With that wish unfulfilled, Kravitz is now left to mourn the musician he deeply admired.
"I am heartbroken," he concluded his post.