Bannon was questioned for hours by Robert Muellers team over the course of two days, CNN said, quoting a person with knowledge of the inquiry.
Bannon responded to all the questions he faced and no areas were off-limits, this person said, according to CNN.
Bannon was a key strategist to President Donald Trump in his "America First" agenda until he left the administration in August.
He also played a key role in the final weeks of the 2016 presidential campaign and took part in transition meetings that are now being examined.
Muellers team were expected to ask Bannon about the firings of FBI Director James Comey and national security adviser Michael Flynn, CNN said.
Disclaimer: No Business Standard Journalist was involved in creation of this content