The chief minister expressed grief over the horrific incident during his meeting with the parents of the victim, a government spokesperson said.
"He also promised to provide all legal help in punishing the culprits and ensuring best medical treatment to Ankit's mother, who has taken ill," he said.
Ankit Saxena was killed in west Delhi's Khyala area on Thursday night allegedly by the family members of a woman with whom he was in a relationship for three years.
The woman's family opposed her relationship with Ankit Saxena, a photographer, as the two belonged to different communities.
The woman's father, mother and uncle have been arrested in connection with the killing. Her minor brother has been held.
Delhi BJP president Manoj Tiwari, who visited Ankit's family on Saturday, had questioned Mr Kejriwal's "silence" over the killing after which he had tweeted that he had spoken to father of the victim.
AAP's Rajya Sabha MP Sushil Gupta and other leaders met the family yesterday on the instruction of the chief minister and assured them of all government help.