He officially announced his intentions of leaving the West Coast Eagles on 2 October 2009. The Eagles then traded Seaby to the Sydney Swans for its second round draft pick (#22 overall) in a complex three-team deal, involving Amon Buchanan who was traded to Brisbane. In the same deal, the Brisbane Lions got Buchanan and Brent Staker and lost Bradd Dalziell to the Eagles along with pick number 28 to the Swans. The Swans also traded their pick number 22 to the Eagles. At the Swans, he was given the number 1 guernsey, previously worn by Barry Hall.