This research was carried out to examine grit as a predictor of chemistry achievement among secondary school students in Kenya. The study was anchored on grit theory developed by Duckworth. The researcher used a correlational research design to establish the relationship between study variables. The target population for the study was 3,320 form three chemistry students in 27 public secondary schools in Etago Sub-County in the year 2023. In this study a sample size of 446 participants were selected from the population using simple random sampling, stratified and purposive sampling. A pilot study involving 30 students from one of the schools within the Sub-County was conducted to refine the reliability and validity of the research instruments. Data were collected using questionnaires and chemistry pro forma forms and then analyzed using the Statistical Package for Social Science (SPSS version 25). The results indicated a significant positive correlation between grit and chemistry achievement, r (433) = .65, p< .05. The study found no statistically significant gender differences in grit in relation to chemistry achievement t (433) = -.39, p = .70. Grit significantly predicted chemistry achievement, F (2,433) = 133.96, p < .05 and its moderation with gender accounted for 5% variance in chemistry achievement. Study recommends that chemistry teachers should enhance effective teaching aids to boost the interest and perseverance (grit) of students during chemistry learning for better achievement in the subject.