Usability is an important aspect of Virtual assembly environment (VAE). This paper presents the evaluation of the usability of our developed multi-sensory VAE. The usability evaluation is in terms of its three attributes: (a) efficiency of use; (b) user?s satisfaction; and (c) reliability in use. These are addressed by using task completion times (TCTs), questionnaires, and human performance error rates (HPERs), respectively. A pegin- a-hole and a Sener electronic box assembly task cases have been used to perform the experiments, using sixteen participants. The outcomes showed that the introduction of 3D auditory and/or visual feedback could improve the usability. They also indicated that the integrated feedback (visual plus auditory) offered better usability than either feedback used in isolation. Most participants preferred the integrated feedback to either feedback (visual or auditory) or no feedback. The possible reasons behind the outcomes are also analysed.