Software outsourcing has been widely adopted by many organisations across industries for producing quality software with reduced cost and faster time to market. Software outsourcing helps organisations overcome the shortage of technical expertise in software development and enables organisations to focus on their core business activities. Despite the benefits, outsourcing also has challenges because the goals of the client and vendor organisations are different. Client organisations use monitoring controls to ensure their goals are met while partnering with vendor organisations. This research focuses on long- term outsourcing partnerships and the nature of organisational changes at client organisations that impact the performance of the vendor team. A qualitative research method is used to gather the insights of selected participants from vendor organisations through semi-structured interviews. The insights are gained from vendor perspectives and the results will be helpful for client organisations to plan the changes along with vendor teams towards successful software projects. The changes in leadership, organisational restructuring, requirement, scaling, and training were identified as the client organisational changes that impact vendor team performance. These changes can be better planned, and the impact can be mitigated by involving vendor team stakeholders in the process and implementation. The magnitude of impact on vendor teams’ performance is dependent on the maturity of the client organisation’s change management process in the identified areas. This study helps client organisations to evaluate their maturity level of change management process in the identified themes and improve for better software project outcomes in partnership with vendor teams.