We consider a design of decentralized control for a class of interconnected non-linear dynamical systems having uncertainty. This uncertainty is (possibly fast) time-varying, and it may appear in each system as uncertain parameter and input disturbance. It also may appear in the interconnections. No statistical information about the uncertainty is imposed; only its possible bound is assumed to be known. The two control schemes proposed here, namely the linear and the non-linear, take the bounds of the interconnections into account. The use of the non-linear control requires more assumptions than the use of linear control. In applications where these assumptions are met, the designers have both controls at their disposal, and depending on the particular application, one may be preferable to the other.