This study investigates the issue of mobility-related teacher turnover in Turkey through both quantitative and qualitative methods. The quantitative findings derived from descriptive and correlational analyses of countrywide teacher-assignment and transfer data indicate that a high rate of mobility-related turnover is observed in the less-developed, eastern provinces of Turkey. The qualitative findings derived from semi-structured, in-depth interviews with school principals suggest that the factors contributing to the issue of mobility-related teacher turnover experienced in eastern Turkey are largely related to the socio-economic and geographic conditions of the region. The qualitative findings further suggest that this turnover issue may have far-reaching negative consequences across school-wide performances and processes. Participants consistently reported that the issue of teacher turnover had negative impacts on student performance, teacher motivation and commitment, instructional planning, administrative processes, and school climate. The study concludes by exploring possible policy implications for alleviating the issue of mobility-related teacher turnover as experienced in the less-developed, eastern regions of Turkey.