Muhammad Waseem, who was arrested late on Saturday, said he gave a "tablet" to Baloch to subdue her and then strangled her in their family home over the weekend.
"I have no regrets," he told journalists in a press conference arranged by the police early on Sunday.
"The police arrested Muhammad Waseem, brother of Qandeel Baloch, for killing his sister late on Saturday," Multan City police chief Azhar Akram told AFP. "Waseem confessed to his crime, saying he killed his sister for honour after her recent objectionable videos, mostly posted on Facebook."
The killing sent shock waves across Muslim Pakistan and triggered an outpouring of grief on social media for Baloch, whose real name was Fauzia Azeem.
In Facebook posts, Baloch, 26, spoke of trying to change "the typical orthodox mindset" of people in Pakistan. She faced frequent misogynist abuse and death threats but continued to post provocative pictures and videos.