Although a lot is known about teacher development by means of formal learning activities, research on teachers' everyday learning is limited. In the current systematic review, we analyzed 74 studies focusing on teachers' informal learning to identify teachers' learning activities, antecedents for informal learning, and learning outcomes. In addition, we examined whether beginning and more experienced teachers differ with regard to informal learning. Results revealed different types of learning activities in the two groups and interesting relationships among different antecedents and various learning outcomes. Moreover, it can be concluded that the main difference between beginning and more experienced teachers lies not in the type of learning activities they undertake but rather in their attitudes toward learning, their learning outcomes, and how they are influenced by their context.