The Australian activist helped the singer kick off her "Matangi" concert tour last Friday night.
"It's a great pleasure to speak to M.I.A. and our fans," Assange told the crowd during his 10-minute speech from the Ecuadoran Embassy in London where he is living in exile. "I have become a fan of M.I.A. because I think she is the most courageous woman working in Western music, without exception."
Rolling Stone said Assange also spoke about press freedom and privacy in the wake of the National Security Agency eavesdropping controversy.
"American journalists that are actually trying to do something really pretty significant -- namely, stop the United States and other countries along with it turning into a military dictatorship slowly, inevitable, inexorably -- they're in exile now," he said. "They've been pushed off to the four corners of the Earth."