This study investigated the effect of using advance organizers on students' motivation to learn biology. The research design used was quasi-experimental design where the non-randomised Solomon Four group was adopted. The focus was on the topic pollution. The sample comprised of 166 form three (third grade in the secondary school cycle) students in Bureti District, Kenya. Data was collected by using Students' Motivation Questionnaire (SMQ). A t-test, one-way ANOVA and ANCOVA statistical techniques were used to analyze the data. The findings indicate that students taught using advance organizers had a higher level of motivation than those taught using conventional teaching methods. The findings further indicate that following the intervention, male students had a significantly higher level of motivation than their female counterparts. This paper concludes by discussing the implications of these findings on current practice. (Contains 7 tables.)