The focus of this study was to investigate teacher-related factors associated with performance in mathematics in public day primary schools in Nandi Central district, Kenya. Seventy-four (74) mathematics teachers participated in the study. Stratified, random, and purposive sampling techniques were used to obtain the samples for the study. Data collection was done using questionnaire which had been validated and subjected to a pilot study to establish its reliability. Each subscale of the questionnaire yielded a Cronbach’s alpha reliability coefficient of 0.60 and higher. The study employed the descriptive statistics and inferential statistic (t-test) to analyze gathered data. The study revealed that the majority of mathematics teachers in Nandi Central district public day primary schools were trained with a teaching experience of between 11–20 years. However, they gave an average rating on the mathematics teachers’ use of learning resources, teaching methodology, teacher preparation, commitment, and assessment and evaluation. Further, teachers in high performing schools rated the attitudes toward mathematics, teaching methodology, commitment, preparation, and use of learning resources, evaluation and assessment higher than their counterparts in the low performing schools. Future research ought to link research on teacher preparation with teacher induction with professional development.