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BackgroundSubthreshold depression has a considerable impact on individuals’ subjective well-being and psychosocial functioning and is a predictor of major depressive disorder. Internet-based cognitive behavioural treatments (iCBTs) have been used to reduce the symptoms of subthreshold depression. This meta-analysis aims to systematically review evidence indicating the efficacy of iCBT programs on the improvement of depressive symptoms in this population.MethodsArticles published from January 2005 to July 2016 were searched in the following databases: Medline, PubMed, Web of Science, ScienceDirect, PsycArticles and the Cochrane Central Register of Controlled Trials. Only randomized controlled trials comparing the efficacy of iCBT programs with control groups for participants with subthreshold depression were selected. Both quantitative and qualitative analyses were conducted to examine the efficacy of iCBT interventions.ResultsTenarticles from 8 randomized controlled trials were identified in this systematic review. The results suggested that iCBT programs had a superior efficacy compared to results from a non-active control group at the post-intervention stage (SMD = − 0.28, CI [− 0.42, − 0.14]; I2 = 49 %). However, evidence on the long-term efficacy of iCBT programs is still insufficient and needs further exploration.ConclusionThere has been substantial evidence that iCBT intervention has a superior short-term efficacy compared to the results of control groups, while its long-term efficacy of iCBT for subthreshold depressive symptoms is inconclusive and must be examined in further research.Trial registrationThe protocol of this review has been registered with the International Prospective Register of Systematic Reviews (PROSPERO), Protocol No. CRD42015023390.