The effects, from a students' perspective, of implementing a multimodal project in a Thai EFL writing class were studied. The research objectives included: (1) examining the effects of the multimodal project on student behavioral engagement, both overall engagement and various interactions, including with peers, the teacher, and the course content, and (2) exploring students' opinions on the use of a multimodal project in the writing class. A quasi-experimental mixed-method design was utilized, with 35 grade-11 students, recruited through purposive sampling, from a school in Bangkok. The research instruments comprised a pre-post student behavioral engagement questionnaire to gauge changes in engagement, as perceived by the students themselves, and a student reflection form to gather qualitative insights from the students regarding their experiences. Quantitative data underwent analysis using descriptive statistics and t-tests, while qualitative data were thematically analyzed. The study revealed a significant increase in overall student behavioral engagement. When examining student behavioral engagement in terms of interactions, the results showed the greatest difference in peer interactions, followed by interactions with the teacher, and then the content. Results from the students' reflections showed positive perceptions towards the utilization of the multimodal project in the writing class. The findings of this study also have implications for teaching writing in EFL contexts.