Background: As many as 9 percent of young people suffer from depression. Unfortunately, many of those who need help remain untreated. The Internet offers an anonymous way to help depressed young people, especially for those who are reluctant to seek help because of fear of discrimination. OBJECTIVE: Our aim was to evaluate the effectiveness of individual chat therapy based on Focused Solution Short Course Therapy (SFBT) for young people aged 12-22 years with depressive symptoms compared to a waiting control group. METHODS: In this study, 263 young people with depressive symptoms were randomly assigned to a web-based focal resolution short-course therapy intervention group (online chat) and a waiting control group. The chat treatment was delivered by trained professionals, and after 9 weeks and 4.5 months, depressive complaints were assessed using a flow call depression scale to compare the differences between the two groups. The online chat group was also assessed for changes in depressive symptoms at 7.5 months after the post-baseline assessment. RESULTS: Compared to the waiting control group (n=132), the SFBT group (n=131) showed more improvement in depressive symptoms at week 9 and 4.5 months on the Streaming Call Depression Scale score, with smaller between-group effect values at week 9 ((d=0.18, 95% CI -0.10 to 0.47) and larger between-group effect values at month 4.5 (d=0.79, 95% CI 0.45-1.08). At month 4.5, the percentage of participants with reliable and clinically significant change in depressive symptoms was also significantly higher in the SFBT treatment group than in the waiting control group (28.2% vs 11.4%, P<.001, number needed to treat=6). At month 7.5, the SFBT group showed a further improvement. However, this result needs to be considered with caution due to the high rate of off-leakage. CONCLUSION: Online chat-based web-based focal resolution short-course therapy was more effective in reducing depressive symptoms than the waiting control group, with greater effects during the follow-up period than after treatment. More studies are needed to confirm whether the results are reproducible, especially for people under 18 years of age. Keywords: depression, randomized controlled trial, internet, focal resolution short-course treatment, young adults