We consider the problem of synchronizing, with prescribed transient and steady-state performance guarantees, the output of high-order, nonlinear, multiagent systems in a leader–following scenario. The agent dynamics are MIMO in lower triangular form and uncertain, as all nonlinearities are unknown and moreover they are perturbed by external additive disturbances. Furthermore, no knowledge is provided regarding bounds or functions bounding the actual system nonlinearities. In addition, the dynamic orders of all agents may not be the same. Each agent utilizes only relative output information from its neighbors and its own state. The underlying communication graph is directed. The proposed control protocol is distributed and of low analytic and computational complexity; thus facilitating implementation. Simulation studies clarify the approach and highlight the theoretical findings.