This study investigated the relationship between principals' conflict management approaches and teachers' job performance in public secondary schools in Keffi Local Government Area (LGA), Nasarawa State, Nigeria. Guided by four specific objectives, the study focused on principals' collaborating, compromising, avoiding, and competing conflict management approaches, as conceptualized in the Thomas-Kilmann Conflict Mode Instrument. The study was anchored on the Thomas-Kilmann Conflict Mode Theory and the Human Relations Theory of organizational management. A correlational survey research design was adopted, with a population of 620 teachers drawn from public secondary schools in Keffi LGA. Using the Taro Yamane formula, a sample of 243 teachers was selected through a multi-stage sampling procedure involving cluster and proportionate simple random sampling. Data were collected using a structured 24-item instrument titled the "Principals' Conflict Management Approaches and Teachers' Job Performance Questionnaire" (PCMTJPQ), validated by experts in educational management and measurement, and found reliable with a Cronbach's Alpha coefficient of 0.81. Research questions were answered using mean and standard deviation, while the four hypotheses were tested using Pearson Product Moment Correlation at the 0.05 level of significance. Findings revealed that principals' collaborating and compromising approaches had significant positive relationships with teachers' job performance, the avoiding approach had a significant negative relationship, and the competing approach had a weak but significant negative relationship with job performance. The study concludes that the conflict management approach a principal adopts substantially shapes teachers' performance, with collaborative and compromising styles yielding the most favorable outcomes. It recommends regular training of principals in collaborative conflict resolution skills and discourages over-reliance on avoiding and competing approaches in school administration.