As a source of social capital, teachers' professional networks have been linked in the research literature with professional learning. Social media platforms have increased teachers' professional networking opportunities, suggesting more space for informal learning. Capturing the experiences of 41 school teachers in Kazakhstan using thematic analysis of semi-structured interviews, the study provides evidence of teachers' use of social media within professional communities to obtain knowledge manifested in an overlapping mixture of news, information, opinion, experience and teaching resources. The study results provide a partial explanation for teachers' engagement in virtual professional communities in the context of informal learning. Highlighting the need for professional connectedness as part of a strong professional commitment to learning, the study points to the contextual factors such as the professional isolation of teachers in rural schools, the need for mentoring support, and the context of educational change. Equally, it stresses the role of teachers' self-efficacy to share knowledge, linking it with opportunities for informal learning of active and passive participants in virtual professional communities. Finally, the study's findings also point to the importance of face-to-face collaboration within and beyond schools to promote professional knowledge exchange within virtual professional communities.