He will play in the four-day County Championship and One-Day Cup.
The left-hander, 30, will join after the Australia A tour of Sri Lanka, which ends on Friday.
He was recruited by former Australian Test cap Marcus North, now Durham's director of cricket.
The Melbourne Renegades captain has played three Tests and six T20 internationals for Australia and scored more than 6,500 first-class runs, including 15 centuries.
"I can't wait to get to the UK and join up with such a great club," said Maddinson.
Maddinson has played for both New South Wales and latterly Victoria in the Sheffield Shield, averaging 40 at first-class level with a highest score of 224 against South Australia.
North said Maddinson was a "very talented overseas signing who offers something with both bat and ball in both red and white ball cricket".
"His record in domestic cricket back in Australia is fantastic, and we are sure he will be a great addition to the Durham squad."
Durham are sixth in the eight-team second division of the County Championship with one win from eight matches. The One-Day Cup is yet to start.
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