Smith, who has played just four Twenty20 internationals for Australia since the start of 2023, went unsold at the Indian Premier League auction held in December last year. He competed for the Sydney Sixers in the 2023-24 Big Bash League (BBL).
He will be reunited with former team mate Ricky Ponting, who was appointed coach of Washington Freedom in February.
Last year, Smith was named brand ambassador to Washington Freedom, who have a high-performance partnership with New South Wales, his domestic team in Australia.
Washington Freedom finished third in the inaugural season of the six-team T20 tournament. The second edition of MLC is set to begin on July 4th, following the conclusion of this year's T20 World Cup in the United States and West Indies.
