Announcing his arrest, SSP Gulab Singh said two country-made pistols were also recovered from his possession.
"We have arrested the prime accused Salman in the Abdul Hakim murder case. Two country-made pistols were also recovered from his possession," Singh said on Thursday.
Police suspect the arms recovered from him were used in the crime, he added.
Hakim, who had married a girl Mahvish against her parents' wishes, had revealed threats to his life from girl's family members during his appearance in Bollywood actor Amir Khan's TV show 'Satyamev Jayate'.
His killing had drawn widespread criticism, compelling the Central government to seek report from the Uttar Pradesh government over the issue.