The 62-year-old Kumar, a 1979-batch IPS officer of the Haryana cadre, retired in September last year after heading the National Investigation Agency, an anti-terror probe organisation, for over four years.
According to an official order, Kumar has been appointed vigilance commissioner in the Central Vigilance Commission for a term of four years or till he attains the age of 65.
The post was lying vacant since February.
According to the rules, Kumar's tenure will come to an end in October 2020.
The Commission comprises central vigilance commissioner and two vigilance commissioners.
At present, KV Chowdary is the CVC and T M Bhasin is the other vigilance commissioner.