Youth smoking continues to be a significant global public health concern. To ensure healthier lives for youths, healthcare professionals need to increase awareness among the youth of the health risks and addictive nature of smoking, strengthen their ability to resist negative peer influence and curiosity, and help those who smoked to quit. The Smoke-free Teens Programme was launched in 2012 to equip youngsters with up-to-date information about smoking and global trends in tobacco control and to encourage them to play a pioneering role in tobacco control. This paper describes the process and outcomes of this programme for youths in Hong Kong.The Smoke-free Teens Programme contained three major components: (i) a 2-day-1-night training camp; (ii) creative activities to promote smoke-free messages in schools and the community; and (iii) an award presentation ceremony to recognize the efforts of outstanding Smoke-free Teens in establishing a smoke-free culture. All secondary school students or teenagers aged 14 to 18 years from secondary schools, youth centres and uniform groups were invited to join the programme. The outcome measures were changes in (1) knowledge about smoking hazards; (2) attitudes towards smoking, tobacco control, and smoking cessation; and (3) practices for promoting smoking cessation.A total of 856 teenagers were recruited during the study period (July 2014 to March 2017). The results showed statistically significant changes in participants' knowledge about smoking hazards, attitudes towards tobacco control, and practice for promoting smoking cessation.The Smoke-free Teens Programme demonstrated effectiveness in equipping youngsters with up-to-date information about smoking and global trends in tobacco control and in encouraging them to play a pioneering role in tobacco control. The trained Smoke-free Teens not only promoted the smoke-free messages among their schoolmates, friends, and families, but also gathered community support for a smoke-free Hong Kong. The programme has been instrumental in fostering a new batch of Smoke-free Teens to advocate smoke-free culture and protect public health.Clinicaltrials.gov ID NCT03291132 (retrospectively registered on September 19, 2017).