Engaging students in the second language (L2) classroom is a critical task that requires a clear understanding of the multilayered characteristics of the L2 classroom and the motivational mechanisms through which these characteristics influence student engagement. This study contributes to the L2 engagement literature in this regard by examining the relationship among students' expectancy and task value belief, their perception of the three L2 classroom conditions, namely classroom structure, teaching relevance, and peer support, and their engagement in an instructed L2 learning setting. Structural equation modelling was employed to analyse self-report data collected from 413 first year students of English as a foreign language (EFL) in Vietnam. Results suggest that teaching relevance and peer support significantly predicted students' expectancy and task value belief, which in turn enhanced all dimensions of engagement. On the other hand, classroom structure was found to have no effect on students' expectancy value belief and their engagement in the L2 classroom. Multi-group analyses further revealed that the effect of teaching relevance on expectancy belief was significant and strong only for high-proficiency students while peer support predicted task value belief more strongly among English major students than non-English major students. The findings offer important implications for the development of an engaging L2 classroom that caters to students with different L2 proficiency levels and academic majors.