Examination of the personal characteristics (i.e., gender, participation styles) of participants and the technical infrastructure (i.e., device type, internet connection type) of Instructional Discussion Forums (IDFs) can provide functional clues for mitigating social anxiety in these settings. In this context, this research investigated variances in learners' participation styles and social anxiety in IDFs in terms of gender and ICT availability. In addition, it explored the predictive relationships between participation styles and social anxiety. A sample of 272 freshman undergraduate students discussed various topics related to Internet ethics for three weeks through an IDF. The results indicated that participation styles differed by gender and ICT availability in several respects. First, handheld devices and cellular internet connections exerted a medium-size effect on social anxiety. Further, "to get information" and "to fulfill requirement" purposes in the "Why" dimension of participation styles had a small predictive relationship with social anxiety, as did "analytical" and "practical" participation approaches in the "How" dimension. Of these, only the "to get information" purpose negatively predicted social anxiety. Overall, participation styles accounted for 19.1% of the variance in social anxiety. Based on the findings, future directions and practical implications are suggested for both researchers and practitioners.