A powerful batsman capable of playing anywhere in the top or middle order, Maddinson has played for Australia at Test and T20I level.
He will join fellow Australian big hitter Aaron Finch at Surrey following the completion of their international commitments against England, Pakistan and Zimbabwe.
The 26-year-old has played two T20Is for Australia, one in 2013 and one in 2014, as well as three Tests during his nation’s 2016/17 series with South Africa.
In addition to eight years with New South Wales in Australian state cricket, Maddinson has played in the Big Bash League for Sydney Sixers, the Indian Premier League for Royal Challengers Bangalore and the Caribbean Premier League for Guyana Amazon Warriors.
In total, Maddinson has played 73 T20s and scored 1549 runs at a strike rate of 130.93 with nine half-centuries to his name.