This paper aims to explore Key Influencing Factors (KIFs) from the perspective of national ERP vendors throughout pre-implementation and during implementation of ERP projects. We conducted a mixed methods study on 10 national ERP vendors involved in government sector projects in Saudi Arabia. KIFs were identified through in-depth interviews and prioritised using a multi-criteria decision analysis method. Findings suggested a list of KIFs that are grouped into four main categories namely sponsors and leadership, IT capabilities, change management and project management. The prioritisation of the KIFs reveals the ERP capabilities and the stakeholder managers to be the most important factors.