Background: In China, depressive disorders have been estimated to be the second leading cause of years lived with disability (YLDs). However, nationally representative epidemiological data for depressive disorders, in particular depressed adults’ mental health services use, are still unavailable in China. The present study is a part of the Chinese National Mental Health Survey (CMHS), 2012–15, which reported the prevalence, treatment, and associated disability of depressive disorders in the Chinese general population. Methods: The CMHS recruited a representative sample of 28140 Chinese residents (≥ 18 years) by using multistage proportional-to-population-size sampling method. Trained investigators interviewed participants with the Composite International Diagnostic Interview 3.0 to ascertain the presence of lifetime and 12-month depressive disorders according to DSM-IV criteria, including major depressive disorder (MDD), dysthymic disorder (DD), and depressive disorder not otherwise specified (DD-NOS). Participants with 12-month depressive disorders were asked whether they ever received any 12-month treatment for their emotional problems and the specific types of treatment providers. The Quick Inventory of Depressive Symptomatology and Sheehan Disability Scale (SDS) were used to evaluate the severity of and role impairments associated with 12-month depressive symptoms. Findings: The weighted lifetime and 12-month prevalence rates of any depressive disorder were 6.8% (95%CI: 5.8-7.8%) and 3.6% (95%CI: 3.0-4.2%), respectively; the corresponding figures were 3.4% (95%CI: 2.0-3.9%) and 2.1% (95%CI: 1.8-2.4%) for MDD, 1.4% (95%CI: 1.1-1.7%) and 1.0% (95%CI: 0.8-1.3%) for DD, and 3.2% (95%CI: 2.6-3.9%) and 1.4% (95%CI: 1.1-1.7%) for DD-NOS. Overall, 77.2% of persons with 12-month depressive disorders had role impairment of any SDS domain: 82.2% for MDD, 81.5% for DD, and 64.6% for DD-NOS. Depressed participants reported an average of 41.0 days out of role in the past year due to depression; the corresponding figures were 49.7 days for MDD, 54.9 days for DD, and 12.2 days for DD-NOS. In total, 88.9% of individuals with 12-month depressive disorders had clinically significant depressive symptoms: 93.7% for MDD, 91.7% for DD, and 77.5% for DD-NOS. MDD and DD had similar proportions of “severe” or “very severe” depressive symptoms (43.0% and 42.1%), which were higher than DD-NOS (13.9%). 9.5% of participants with 12-month depressive disorders were treated in any treatment sector: 3.6% in the specialty mental health (SMH), 1.5% in the general medical (GM), 0.3% in the human services (HS), and 3.3% in the complementary-alternative medical (CAM) sector. Respondents with MDD and DYS had the highest proportion of seeking treatment in SMH sector (4.7% and 3.0%) while those with DD-NOS had the highest proportion of seeking treatment in CAM sector (most treatments were Traditional Chinese Medicine) (3.3%). Only 0.5% of participants with depressive disorders were treated adequately. Rates of treatment adequacy of MDD and DYS in SMH sector were 9.2% and 2.4%, respectively. Both rates in GM sector were 0%. Interpretation: Compared to western countries, our data show a relatively low prevalence of depressive disorders in China. Nevertheless, their associated role impairments, symptom severities, and disabilities are severe. Importantly, the treatment rates are rather low, let alone adequate treatment. Nationwide programs aiming at removing barriers in availability, accessibility, and acceptability to mental healthcare are needed in China. Funding: The study was funded by the Special Research Project for Non-profit Public Service of the Chinese Ministry of Health (grant number 201202022), the National Twelfth Five-Year Plan for Science and Technology Support of the Chinese Ministry of Science and Technology (grant numbers 2012BAI01B01 & 2015BAI13B00) and the National Key R&D Program of China (grant numbers 2017YFC0907800, 2017YFC0907801). Declaration of Interests: The authors have no conflicts of interest to declare Ethical Approval: The study protocol of CMHS was approved by the Ethics Committee of the Sixth Hospital of Peking University (No.: IMH-IRB-2013-13-1).