This paper deals with an adaptive H_∞-control for the Lagrangian systems with the visual feedback in presence of parametric uncertainties. Based on an adaptive manipulator control, the proposed controller consists of the visual PD feedback part and the full dynamics feedforward part with the update law of the parametric uncertainty. The L₂-gain performance analysis of the proposed controller is carried out and its asymptotic property is examined. For the L₂-gain performance analysis, the image feature parameter potential plays an important role as the storage function.