Extensive research on student motivation has collectively pointed to the strong correlation between motivation and learning. However, very little is known about Vietnamese students’ motivation. This exploratory study directly addresses this gap in knowledge, focusing on the development of an overall picture of the academic motivation of Vietnamese tertiary students.Deci and Ryan’s (1985, 2002, 2008) macro theory of motivation, self-determination theory (SDT), has been extensively used to better understand educational outcomes. With its component mini-theories recognising both internal and external sources of motivation, SDT provides a comprehensive framework to study student motivation. As maintained by SDT, motivation quality is more important in predicting behavior and outcomes than the overall quantity of motivation. The quality of student motivation determines how students interact with the learning environment to acquire new knowledge and skills. Thus understanding students’ motivation will help foster students’ engagement in learning, hence better educational outcomes.Based on SDT, the Academic Motivation Scale (AMS) (Vallerand et al., 1992) has been widely used in motivation research on tertiary student populations. The AMS assesses students’ motivation to go to college. The seven AMS subscales include three types of intrinsic motivation, three types of extrinsic motivation, and amotivation. A high score on any subscale is indicative of a high level of that type of motivation. The AMS has been validated in different cultures, including Asian collectivist-oriented cultures. The majority of these validation studies confirm the seven-factor structure of the scale with only minimum acceptable fit indices. However, their findings differ regarding the simplex pattern of the scale.Using responses to the AMS from over 600 Vietnamese tertiary students, this paper explores the factor structure of the AMS in a Vietnamese population. Confirmatory factor analysis was performed in AMOS. Results support the seven-factor structure but also identify several inappropriate items for this population, with cultural explanations supporting these findings. Model fit indices were found to be at an acceptable level with residuals unexplained. Explanations for this investigation as well as previous validation studies include the fact that the subscales do not measure the same underlying factor. The finding that the simplex pattern of the AMS is only partially supported is in line with SDT that motivation types are not exclusive but instead can be present in various combinations.