The aim of this study was to investigate the associations between preservice teachers' Web 2.0 competencies and their critical thinking disposition (CTD). The study employed an associational research design using California Critical Thinking Disposition-Inventory (CCTD-I) and a Web 2.0 competency questionnaire including items related to Web 2.0 awareness, Web 2.0 use, and educational use of Web 2.0 tools. Five different Web 2.0 tools included in the study: (a) blogs, (b) wikis, (c) social networking websites, (d) YouTube, (e) podcasts. A total of 1,335 preservice teachers completed the survey. Findings indicated that participants had a medium level internet use, Web 2.0 awareness, Web 2.0 use, and Web 2.0 skills while their educational Web 2.0 use level was low. In terms of competencies on certain Web 2.0 tools, their blog, wiki, and podcast competencies were at a very low level, whereas their social networking and YouTube competency levels were high. Findings also showed that there were significant relationships between preservice teachers' Web 2.0 competencies and their critical thinking disposition. The results highlighted that the use of different Web 2.0 tools can be complementary to each other during certain instructional activities to improve different dimensions of critical thinking disposition.