Project BP.A.T.H.S.^has been shown to be effective in promoting positive development outcomes among Chinese adolescents in the school context. However, little is known whether the benefits can also be found in other settings. The purposes of the study was to investigate the changes in psychosocial outcomes among Hong Kong Chinese adolescents after participating in a community-based positive youth development (PYD) program. Using a one-group pretest-posttest design, junior high school students (N = 17,544) were invited to join the universal prevention program (the Tier 1 Program) and/or the selective prevention program (the Tier 2 Program). 10,807 students whose pre-and post-test data were successfully matched. The students responded to validated outcome measures assessing PYD outcomes, life satisfaction and thriving at pretest and posttest. Consistent with the hypotheses, students showed positive change on different developmental outcomes after joining the program. Amongst the different programs, students in the Tier 2 Program had significant improvement in all developmental outcome indicators. While limitations of the one-group pretest-posttest design and the alternative explanations are duly acknowledged, the present study suggests that the community-based Project P.A.T.H.S. is a promising approach to promote positive youth development, life satisfaction and thriving of adolescents, a conclusion which is consistent with the existing evaluation findings of the project. Building from previous school-based research, the present study extends the literature by showing the effectiveness of a positive youth prevention program in a community context. Limitations of the study design (e.g., an absence of a control group) are discussed.Applied Research Quality Life