The Delhi pacer failed to attract any buyer at the auction in February.
"I share a strong bond with Ishant Sharma as he played under my captaincy in the Ranji Trophy and later in the India team, his addition will most definitely strengthen our squad," Virender Sehwag, Kings XI's head of cricket operations, stated in a release.
Kings XI's pace attack already comprises Mohit Sharma, Sandeep Sharma, Varun Aaron, Anureet Singh, Matt Henry and T. Natarajan, who was bought for Rs 3 crore at the auction.
Kings XI play their first match on April 8, against Rising Pune Supergiant, the franchise Ishant represented last season.
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