Moodle is applied as an online learning management system in the Faculty of Medicine, Thammasat University (TU), where the curriculum has been based on problem-based learning (PBL) since 2015. Little research on the effectiveness of Moodle and students’ attitudes during their studies at the pre-clinical medical level within a PBL curriculum has been conducted. Hence, this cross-sectional study focuses on second- and the third-year (MD-2 and MD-3) preclinical medical students’ attitudes towards Moodle and its effectiveness in the PBL curriculum by using a 27-itemed self-constructed online questionnaire. Additionally, students’ preferences as regards the materials managed by the Moodle platform were also evaluated as students’ preferred behaving style (SPBS). After obtaining ethical approval from the Human Ethics Committee of TU No. 1 (Faculty of Medicine), the data was collected and analyzed by medians and inter-quartile ranges, Mann-Whitney U test, and Spearman correlation (