In their everyday work, scholars constantly acquire and transfer knowledge. Many of these knowledge flows are difficult to observe, not least because scholars are often not aware of them. This may be the reason why the attention to knowledge flows is very unevenly distributed across science studies, with bibliometric citation-based studies contributing the most research. Starting from the premise that bibliometric methods can be more readily exploited in the study of knowledge flows, this review explores the potential of bibliometric methods for the investigation of knowledge flows. Bibliometrics provides a portfolio of data and methods that can be used alone or in combination with qualitative methods to study knowledge flows. We organise contributions to the study of knowledge flows according to their object of study--formal, informal, or tacit knowledge--and according to the mode of flow--impersonal or interpersonal knowledge flow. The review shows that bibliometrics is strongly focused on the use of citation data for the investigation of impersonal flows of formal knowledge and has recently turned to the impersonal flow of informal knowledge via social media. In contrast, there are only few bibliometric studies that address interpersonal flows of knowledge. The review identifies an under-utilised potential of bibliometric methods and suggests some directions for future methodological development.