Purpose: Multimodal writing portfolios were introduced and integrated into an undergraduate course and a graduate course in a research-oriented university in northwest Taiwan. This study aims to examine the influence of multimodal writing portfolios of novice researchers' academic writing. Design/methodology/approach: Comparative case studies involve collecting data from several cases and analyzing the similarities, differences and patterns across cases (Merriam, 2009). To address this underdeveloped area of research, a comparative case study method was employed to understand undergraduate and graduate students' multimodal writing portfolios in academic writing in two courses in Taiwan. Findings: First, multimodal writing portfolios enabled novice researchers to be more familiar with the structure of academic paper and they had better performance in intrapersonal and linguistic aspects. Second, novice researchers held positive attitude toward multimodal writing portfolios because they regarded process of making multimodal writing portfolios as preparation for their future academic writing. Finally, participants highly valued the class PowerPoint slides, weekly writing tasks and the instructor's modeling as effective facilitation for making multimodal writing portfolios. Research limitations/implications: Limited studies focus on multimodal writing portfolios (e.g. Silver, 2019). The present case study explores the integration of a multimodal writing portfolio into one undergraduate and one graduate course to explore learners' attitude and performance in academic writing. Practical implications: Novice researchers can learn to compose multimodal academic texts for the academic writing community. Social implications: Suggestions on effective integration of multimodal writing portfolios into academic writing instruction were provided based on the research findings. Originality/value: The findings of the study provide the field of L2 writing with insights into the pedagogical development of multilingual writing portfolios and help educators to be better prepared for teaching novice researchers to comprehend and compose multimodal texts and enter the academic writing community. The framework in Figure 1 and suggestions on course designs for academic writing can inform educators on the integration of multimodality in academic discourse. Moreover, this study moves beyond general writing courses at the tertiary level and could contribute to L2 writers' deeper understanding of how multimodal writing portfolios can be constructed.