The purpose of this study was to examine the relationship between teachers' self-efficacy in using of Web 2.0 tools and some demographic variables, and their use of those tools in their teaching. The study data was collected from a random sample of public school teachers in Riyadh, Saudi Arabia. The results showed a strong positive relationship between teachers' Web 2.0 self-efficacy beliefs and their actual use of Web 2.0 tools in classroom teaching. Moreover, the study found that in-service training, age of teachers, and access to Web 2.0 tools at school had a strong relationship with teachers' use of Web 2.0 tools in teaching. The study recommended the need to intensify in-service training for teachers in the use of modern Internet tools in teaching.