The Italian joined the club in the summer of 2012, and will take command of his teammates after the board decided to restrict the responsibilities of coach Victor Munoz.
The Swiss side has been on a poor run of form of late, and the club's board have decided to hand extra responsibility to the players in the wake of their 4-0 loss to Thun over the weekend in a bid to reignite their ambition.
"After the disastrous performance of Sion at Thun and in face of the obvious lack of direction of the team, the management of the club has decided to put the players in front of their responsibilities," a club statement read. "To do this, from today, and until further notice, they will take care of their own affairs. The management is assigning hierarchical responsibility of the group to campaign Gennaro Gattuso.
"Victor Munoz, meanwhile, has taken a step back. With this decision and the measures imposed, the club's management hopes to improve the performance of the team rapidly and the investment of the leading figures, who no longer have the ambition of the club."
Gattuso signed for Sion last summer after leaving the San Siro on a free transfer.