The present study investigated the extent to which extrinsic motivation beliefs predicted academic achievement in chemistry among students in public secondary schools in Kenya. The study was guided by Eccles-Wigfield’s Expectancy-Value theory of motivation. Concurrent embedded design was used in the study. Both Stratified random sampling and purposive sampling techniques were used to select 351 form four students, 10 chemistry teachers and 10 guidance and counseling teachers who participated in the study from the 26 sampled schools in Rachuonyo South sub County, Homa Bay County, Kenya. Questionnaires and interview schedules were used for data collection. Quantitative data was analyzed both descriptively and inferentially while qualitative data was analyzed using thematic analysis. The finding of the study showed that there was statistically significant, though weak, positive correlation (r=.274, n=308, p<.05) between extrinsic motivation beliefs and chemistry academic achievement and extrinsic motivation accounted for only 7.5% (R Square =.075) of the variation in performance in chemistry in KCSE exams. Based on findings, the study recommended that for the purposes of enhancement of motivational beliefs like extrinsic motivation, school principals should arrange for workshops and seminars for chemistry teachers to help chemistry teachers develop skills which are essential for helping students enhance such motivational beliefs. This is because extrinsic motivation beliefs had positive, though weak relationship with chemistry academic achievement.