The 26-year-old winger will be expected to play an important role in the Owls’ quest to get promoted to the Premier League.
Carlos Carvalhal’s side will be aiming to finish at least in the top six of the Championship this season.
The 26-year-old has struggled to establish himself in the Sunderland first team and was on loan at two different clubs last season.
The winger played on loan for Leeds for a spell during the first half of the 2015-16 campaign before joining Championship rivals Birmingham City on loan in the January transfer window.
During his loan spell at Elland Road, Buckley could feature in just four Championship matches and was a disappointment.
Leeds and Wednesday fans have taken to social networking site Twitter to give their reaction to the transfer of Buckley.
Below are some of the best comments:
Sheffield Wednesday fans on Will Buckley:
Intrigued to see how Buckley plays for us, surely he'll be preferred to Sougou? #SWFC— Pat (@Pat_Stothard) 5 August 2016
If Buckley can rediscover his Brighton form he will be a great signing. Westwood extending contract is brilliant. Good day at #swfc— WarOfTheMonsterTruck (@SheffWedWOTMT) 5 August 2016
Buckley another very canny acquisition. Previous experience at Championship level. More competition for shirts and rotation. #swfc— Simon Rodgers (@simontheowl6) 5 August 2016
Leeds United fans on Will Buckley:
I bet Will Buckley absolutely smashes it at #swfc Typical.— AlwaysLeedsUnited (@AlwaysLeedsUnit) 5 August 2016
Lufc_shaun) 5 August 2016
Sheffield Wednesday manager Carlos Carvalhal