Rahul Sharma had a narrow escape when he was targeted by bikers on a busy road at Greater Noida near Delhi, said the police.
Mr Sharma's car was overtaken by a bike at a roundabout and the attackers tried to fire at his car but the pistol apparently misfired.
The activist hit the bike and drove off from the spot, the police said. He was with his cousin when the incident took place.
The attack was caught on CCTV and a police complaint has been filed.
Mr Sharma had alleged that Mr Kejriwal's brother-in-law Surender Kumar Bansal, who died last month, swindled the Delhi Government by manipulating contracts for laying roads and sewer lines in the capital.
Fake bills and invoices were also cleared, he alleged, accusing Chief Minister Kejriwal and minister Satyendra Jain of misusing their offices to grant contracts to Mr Bansal.
The Delhi Anti-Corruption Branch recently recorded the statements of Mr Sharma, who runs an NGO.
Three cases were filed by the Anti-Corruption Branch against Mr Bansal and others.
Mr Sharma has alleged death threats in the past.
Aam Aadmi Party (AAP) spokesman Vaibhav Maheshwari said his party had nothing to do with the incident and "this is not our brand of politics".
He also said that the police should get to the bottom of the incident and arrest those involved.