Microblogging tools such as Twitter show potential to enrich classroom experience and benefit student learning. Research shows that instructional guidance is particularly necessary in computer-assisted learning environments, but no research has been done to study the effects of instructional guidance in microblogging-based learning. Using a multiple-case study design, the researcher examined student learning in terms of the amount of participation, ability to focus on task, and depth of thinking in guided, semi-guided, and unguided modes. The findings suggest that in guided environments, students achieved higher levels of learning, especially with respect to focusing on task and depth of thinking. Variations in depth of learning existed between the semi-guided and the guided mode. Students' perceptions of the benefits and challenges of using microblogging across three cases were also analyzed. The study has implications for future research on using microblogging tools for educational purposes and pedagogical practice.