New-type drugs are popular with adolescents and could lead to psychiatry disorders, but no medications have been proven to be effective for these disorders of new-type drug dependence. We aimed to evaluate the efficacy of tryptophan on sleeping disorders and mental symptoms in detoxified individuals with new-type drug dependence. This randomized, placebo controlled trial included 80 detoxified individuals with new-type drug dependence, recruited successively from a Compulsory Residential Drug Abstinence Institution in Wuhan, China, from April 2012 to November 2012. Eligible participants were randomly allocated to be treated with tryptophan (1000mg/day, n=40) or placebo (n=40) for two weeks. The sleeping and mental symptoms were assessed using Athens Insomnia Scale (AIS) and Symptom Check-List-90 (SCL-90) at baseline and two weeks. Results were analyzed according to the “intention-to-treat” approach. Forty-five participants completed the two-week study, 24 in the tryptophan group and 21 in the placebo group. There were no statistically significant differences in baseline characteristics between groups and the treatment adherence was similar between groups. The reduction in the Athens Insomnia Scale (AIS) score in the tryptophan group was significantly greater than that in the placebo group (P=0.017). However, no significant differences were found in Symptom Check-List-90 (SCL-90) scores (either by individual dimension or the overall score) between groups (all P>0.05). The frequency of adverse events were similar and no serious adverse events were reported during the study. Tryptophan was unlikely to be effective for mental symptoms, but could alleviate sleep disorders in short term among detoxified individuals with new-type drug dependence. Future large scale trials are required to confirm findings from this study.