CONTEXT: There is limited research on the gap between the burden of mental disorders and treatment use in low- and middle-income countries. OBJECTIVES: The aim of this study was to assess the treatment gap among adults with depressive disorder (DD) and alcohol use disorder (AUD) and to examine possible barriers to initiation and continuation of mental health treatment in Nepal. METHODS: A three-stage sampling technique was used in the study to select 1,983 adults from 10 Village Development Committees (VDCs) of Chitwan district. Presence of DD and AUD were identified with validated versions of the Patient Health Questionnaire (PHQ-9) and Alcohol Use Disorder Identification Test (AUDIT). Barriers to care were assessed with the Barriers to Access to Care Evaluation (BACE). RESULTS: In this sample, 11.2% (N = 228) and 5.0% (N = 96) screened positive for DD and AUD respectively. Among those scoring above clinical cut-off thresholds, few had received treatment from any providers; 8.1% for DD and 5.1% for AUD in the past 12 months, and only 1.8% (DD) and 1.3% (AUD) sought treatment from primary health care facilities. The major reported barriers to treatment were lacking financial means to afford care, fear of being perceived as "weak" for having mental health problems, fear of being perceived as "crazy" and being too unwell to ask for help. Barriers to care did not differ based on demographic characteristics such as age, sex, marital status, education, or caste/ethnicity. CONCLUSIONS: With more than 90% of the respondents with DD or AUD not participating in treatment, it is crucial to identify avenues to promote help seeking and uptake of treatment. Given that demographic characteristics did not influence barriers to care, it may be possible to pursue general population-wide approaches to promoting service use.