South Africa lags behind in terms of competing globally in science and technology. Thus, the purpose of the study was to investigate teacher factors that influenced learners' motivation to learn science in a secondary school. The study also aimed to determine whether significant differences in motivation regarding teacher influence existed among age groups and genders. The research was conducted in a public secondary school in Gauteng province, South Africa with 462 learners from Grade 8 to Grade 11. Using a quantitative approach, the learners completed a questionnaire that involved several motivation constructs (mastery and performance goal oriented). The study identified some problems that could impact on learner motivation and also found that some significant differences existed among different grades and genders. A number of recommendations were made regarding the teacher's role in motivating science learning.