The three year deal - commencing in 2014-15 - will see all the club's teams being provided with playing and training wear, as well as replica retail wear.
Neil Burke of Sports Direct expressed his pride in the partnership and the excitement at the prospect of "two major sporting brands uniting.'
Sheffield Wednesday's Peter Pridmore reiterated Burke's words, and stressed that the Owls would be “viewed as Sondico's flagship club for 2014-15" and that they would be provided with a "bespoke range of designs.''
Wednesday were previously with Puma.
Sondico has become a major player in the team wear market, and already supply a range of Football League teams, including MK Dons.