This paper presents an evaluation of Voice over IP (VoIP) system level performance in High Speed Downlink Packet Access (HSDPA) network. The main purpose is to determine how VoIP over HSDPA performance is affected by HSDPA handover i.e. serving High Speed Downlink Shared Channel (HS-DSCH) cell change. This paper studies how sensitive the capacity of VoIP service is to handover delay and User Equipment (UE) velocity. Additionally, the reliability of handover related signaling in downlink is evaluated. The system level performance of VoIP in the mobility related scenarios is evaluated with fully dynamic system level tool in which mobility of users, radio resource management functionalities and the interactions between them are explicitly taken into account. The simulation results indicated moderate sensitivity of VoIP capacity to the UE velocity. High velocities lead to capacity loss for VoIP over HSDPA. Handover delays started to have significant effect only at UE velocity of 50 km/h or more. Reliability of handover signaling does not pose any problems even at high velocity and incurs only 1% resource overhead when transmitted over HSDPA.