Mental health literacy (MHL) refers to knowledge and attitudes that shape the recognition, management, and prevention of mental disorders. While the topic has been exhaustively researched in Western countries, research from Southeast Asia still is limited. Previous studies in this field showed a moderate recognition of mental disorders, a high prevalence of stigmatizing attitudes and a low willingness to seek professional help among Southeastern-Asian populations. This study explored the level of MHL among university students from different parts of Vietnam and Cambodia. Correlations with influencing factors (gender, age, study year, educational attainment of the parents, urban/rural origin, ethnicity, personal experiences with mental disorders) were also explored. An online survey, using a 30-item Vietnamese version of the Mental Health Literacy Scale (MHLS), was conducted at six university sites in Vietnam and Cambodia. Data of 1032 students from different study branches were included. The MHL of Vietnamese and Cambodian university students was lower, compared to samples from Australia or the UK. Females and students with a personal experience of mental disorders (self or family) showed a significantly higher MHL. No differences in MHL were found between students from different socioeconomic backgrounds (professional attainment of parents, urban/rural origin). Findings on the influence of ethnicity were inconclusive. MHL needs to be improved among the university students of Vietnam and Cambodia. Mental health promotion should specifically target male students, students from STEM branches, and international students.