The disqualification must be revoked, Mr Kejriwal said.
"Disqualification of Sharad Yadav ji is completely illegal and unconstitutional. It is political vendetta. We strongly condemn it and demand that disqualification be revoked," Mr Kejriwal tweeted.
Rebel JD(U) MPs Sharad Yadav and Ali Anwar were disqualified from the Rajya Sabha on Monday night.
Rajya Sabha Chairman M Venkaiah Naidu agreed to the JD (U)'s contention that the two senior leaders had "voluntarily given up" their membership by defying their party's directives and attending events of opposition parties.
The JD(U) had sought their disqualification on the grounds that they had attended a rally of opposition parties in Patna in violation of its direction.
Mr Yadav had joined hands with the opposition after JD(U) president and Bihar Chief Minister Nitish Kumar dumped the Grand Alliance in Bihar and tied up with the BJP.
Sharad Yadav was elected to the House last year and his term was scheduled to end in 2022. Mr Anwar's term was to expire early next year.