The purpose of this study was to evaluate the performance of voice over IP and video over IP on IP transition mechanisms and clarify the impact of each IP transition mechanism on voice and video transmission under different environments. Studies conducted predicted that IPv4 will soon run out of IP addresses and IPv6 will be the future communication protocol of choice. However, IPv6 still has a challenge ahead, since it does not communicate with IPv4 directly. This issue needs to be resolved prior to establishing IPv6 networks. The migration from IPv4 to IPv6 will take several years, as it is highly complex and expensive for all users around the globe to make a switch. Researchers have developed several methods called IP Translation, Tunnelling and Dual-Stack mechanisms, which allow IPv4 and IPv6 to communicate with each other. In this study, performance of voice and video was measured and analysed on different IP transition mechanisms on a network environment created in a laboratory. This study was carried out in three parts. First part includes; VoIP performance on three IP transition mechanisms using five different platforms. Second part relates to performance comparison of VoIP over pure IP version 4 and IP version 6 with IP transition mechanisms using five voice CODECS. Third part includes; impact of IP transition mechanisms on video protocols. Main focus of this research was to identify the impact caused by IP transition mechanisms on VoIP and video over IP. The results obtained for VoIP showed that performance of VoIP on Windows 7 OS using the three IP transition mechanisms performed much better as compared to the other four operating systems. Observation of packet-loss indicated that Windows based OSs had higher packet loss while Linux based OSs had lesser packet loss over all five CODECS for VoIP trials. Results compiled for delay indicated that IPv6-to-4 and IPv6-in-4 marginally performed better than Dual-Stack mechanism. Video over IP transition mechanisms confirmed that video protocols were highly impacted by encapsulation and de-capsulation process except where FLV protocol was used. FLV was the least impacted by IP transition mechanisms. It also indicated that using IPv6-to-4 and IPv6-in-4 tunnelling mechanisms caused more bandwidth wastage than Dual-Stack mechanism.