Introduction: Smoking among adolescents remains a major concern because of its long term health hazards. An effective adolescent-specific anti-smoking education is needed. Objectives: To measure the impact of a school-based tobacco prevention program provided by pharmacists on the attitudes and knowledge of senior high students. Methods: An anti-smoking program specifically aimed at high school students was developed by pharmacists and introduced to 354 students inTaiwan. It consisted of a role play and a lecture. The students were asked to complete a structural questionnaire right before and after the intervention. Results: After the intervention, the average of the total attitude scores increased from 41.7 to 43.2 (p = 0.001), and the total knowledge scores increased from 6.4 to 8.2 (p < 0.001). The average practice score was 31.2 (maximum score = 50) and the result suggested that the practice score was associated with attitude rather than knowledge. Conclusion: This pharmacist-conducted anti-smoking program for high school students resulted in positive changes regarding both attitude and knowledge. This suggests that further anti-smoking programs targeting students would be effective in helping to prevent youth smoking.