Video clubs, in which teachers meet to view videos of their classrooms in order to improve instruction, have become a popular means of professional development. With today's technology, these video clubs can be conducted virtually, yet little is known about the effectiveness of asynchronous or synchronous virtual video clubs. This study addressed how districts and schools can support teachers with effective, job-embedded professional development within the confines of teachers' busy schedules using asynchronous or synchronous virtual microteaching video clubs. A mixed-method approach was used to explain the effectiveness of teacher learning in each video club setting in terms of the conversations in the video club as well as the ease of scheduling the video club for participants. An explanatory quasi-experimental mixed-method study was conducted in which teacher participant groups were randomly assigned to an asynchronous or synchronous setting for the video club. The data collected consisted of transcripts of the video club conversations, an ease of scheduling survey, and a posttest and retrospective pretest to determine the effectiveness of participants' learning. Both settings were found to have high effect sizes and significant differences between the retrospective pretest and posttest scores, with higher effect sizes for the synchronous setting. However, the null hypothesis regarding a difference in pretest and posttest scores between settings failed to be rejected. The themes emerging from the scheduling data included a focus on both the benefits and challenges of the flexibility of the asynchronous setting and both benefits and challenges to the routine nature of the synchronous setting. The themes emerging from the conversation transcripts were a focus on learning from each other in the asynchronous setting versus learning with each other in the synchronous setting. The results and findings demonstrated the potential effectiveness of virtual video clubs in both settings. Additionally, the qualitative data suggested explanations for the lower effect size of the asynchronous setting and how to improve it: effective asynchronous learning spaces should be set up with expectations for the participants that are monitored by an administrator, and discussion boards should be used in a way that leads to less monological and more dialogical discussion. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]