Purpose: Student in-class participation is a crucial aspect in the learning process, including in synchronous learning process. Several variables may hinder students from actively participating in synchronous learning including communication anxiety. As behavior, student in-class participation can be modeled using theory of planned behavior (TPB) with communication anxiety as barrier variable. The current study aims to investigate student decision-making process to actively participate in synchronous online learning using TPB frameworks and examine the effect of communication anxiety as part of extended TPB. Design/methodology/approach: This was quantitative nonexperimental research conducted by gathering cross-sectional data through electronic survey. A total of 1,009 Indonesian college students voluntarily participate in the survey. Structural equation modeling was used to analyze the data and test the hypothesis. Findings: The results indicate that there was significant and positive effect between TPB-related variables--(1) attitude, (2) subjective norms, (3) behavioral control, (4) intention and (5) behavior. Communication anxiety, as an additional variable in the extended model, shows significant and negative effects on behavioral control and active participation behavior. However, the communication anxiety indicates insignificant effect on students' intention to participate in online synchronous learning. The findings support the evidence that students' intention to actively participate in synchronous learning can be described using TPB and communication anxiety hinders student to actively participate in synchronous learning. Originality/value: The paper extends TPB on student active participation. Prior research limited to original theory of planned behavior (TPB) on student in-class and massive open online course (MOOC) participations, whereas the current research includes communication anxiety as additional variable on extended TPB to understand students' intention to actively participate in synchronous online learning.