Voluntary staff turnover is becoming increasingly common, especially in the IT sector. It can impact job performance and the factors which shape it, such as work motivation. Given this fact, the aim of this paper is to empirically verify the impact of voluntary staff turnover on job performance and work motivation of employees in the IT sector and to verify whether voluntary staff turnover can be a moderator of the relationship between work motivation and job performance of employees in the IT sector. The formulated research hypotheses were verified on a sample of 151 employees from organisations within the IT sector in Poland. To verify the impact of voluntary staff turnover on work motivation and job performance, a correlation analysis was conducted. In order to verify the moderation effect, a regression analysis with a moderator was used. The results of the research reveal that voluntary staff turnover has a negative impact on the job performance of employees from the IT sector. Moreover, voluntar staff turnover is a moderator for the relationship between work motivation and job performance of employees from the IT sector and has a negative impact on this relationship, which means that an increase in voluntary staff turnover reduces the positive impact of work motivation on job performance for employees from the IT sector. In this way, it has been proven that – in terms of impact of work motivation on job performance – the phenomenon of voluntary staff turnover is a negative one, although it is common among employees from the IT sector.