"I probably will be bringing a lot of litigation against a lot of people having to do with the corrupt investigation having to do with the 2016 election," Trump said.
Trump said the Mueller investigation had destroyed the lives of people with a "phony charge that never existed."
Mueller issued a final report on his inquiry in April, saying the probe had found no evidence of collusion between Trump and Russia during the 2016 presidential campaign.
House Democrats have recently launched impeachment proceedings against Trump, saying he sought to pressure Ukrainian President Volodymyr Zelenskyy to investigate Joe Biden's son for possible corruption. Democrats say the request amounted to an attempt to solicit foreign influence in the upcoming US election.
Trump denies any wrongdoing and has accused Democrats of launching another "witch hunt" against him after failing to oust him from office with the Mueller probe.