The actin cytoskeleton is conserved among all eukaryotes and plays essential roles during many cellular processes. It forms an internal framework in cells that is both dynamic and well organised. The plethora of functions ranges from facilitating cytoplasmic streaming, muscle contraction, formation of contractile rings, nuclear segregation, endocytosis and facilitating apical cell expansions. Oomycetes are filamentous organisms that resemble Fungi but are not related to Fungi. The two groups show significant structural, biochemical and genetic differences. One prominent lineage within the class of oomycetes is the genus Phytophthora. This genus comprises over 100 species that are all devastating plant pathogens threatening agriculture and natural environments. The potato late blight pathogen Phytophthora infestans was responsible for the Irish potato famine and remains a major threat today. Previously the actin organization has been studied in several oomycetes. Next to the common F-actin filaments and cables, cortical F-actin containing patches or plaques have been observed as in Fungi. However, only a static view was obtained. Here, we use an in vivo actin binding moiety labelled to a fluorescent group to investigate the actin cytoskeleton dynamics in hyphae of P. infestans. Our results provide the first visualisation of the dynamic reorganization of the actin cytoskeleton in oomycetes. In the future, this line will provide insight in the role of the actin cytoskeleton during infection.