Kumar is the second BJP leader to issue legal notice to the AAP leader after former party President Nitin Gadkari.
The notice served through Kumar's lawyer has asked Kejriwal to withdraw his statements within three days, failing which legal action will taken against him.
"I will initiate appropriate civil proceedings against Kejriwal for compensation and appropriate criminal proceedings against him for libel and slander," he told reporters at crowd sourcing programme conducted by BJP here.
Kejriwal yesterday had called Kumar as "corrupt" and included his name in the list of "Most Corrupt" and said his party would field candidates against him.
He said the allegations levelled by Kejriwal are "motivated, baseless and malicious and their publication is clearly defamatory" and he had failed to provide any shred of evidence to support his allegations.