The information technology industry is characterized by high employee turnover. Previous research on employee turnover has focused on elucidating the antecedents of turnover and suggesting staff retention strategies. However, little research has been devoted to studying how the undesirable effects of IT turnover can be mitigated. As a result of turnover, information system development (ISD) teams face the danger of losing knowledge through personnel departure and difficulties when new members with different experience enter. This study views employee turnover in ISD project teams from the perspective of organizational forgetting. We propose a theoretical model that assesses the negative effect of member turnover on ISD project performance and suggest possible mechanisms for mitigating such effect based on the framework of organizational forgetting. 151 project teams were surveyed and results showed that turnover weakens ISD project performance. However, the use of succession planning, knowledge repository, and employee orientation program to manage different types of organizational forgetting can effectively mitigate the detrimental effects of turnover. Implications for research and practice are discussed.