Assange's show, "The World Tomorrow," premiered Tuesday on Russia Today's English, Arabic and Spanish channels, as well as RT America.
Nasrallah taped his part of the interview remotely from an undisclosed location in Lebanon.
"RT is rallying a global audience of open-minded people who question what they see in mainstream media and we are proud to premiere Julian Assange's new project. We provided Julian a platform to reach the world and gave him total editorial freedom. He is absolutely the right person to bring alternative opinions to our viewers around the globe," RT's Editor In Chief Margarita Simonyan said in a statement.
"When we look at international networks there's really only two that are worth speaking about, and that's RT and al-Jazeera," Assange said. "When we were looking at what international broadcaster... We wished to partner with, we looked to see what was the penetration into the United States. RT had greater penetration into the United States."
Ten episodes of the interview program have been scheduled, at 26 minutes each. The show is being taped in London.
Assange, the Australian founder of WikiLeaks, has spent more than a year under house arrest in the British capital while he battles an extradition request from Sweden where he is accused of sexually abusing two women. He has denied any wrongdoing.